System and method for predictive fault mitigation for electric power steering systems in vehicles
阅读说明：本技术 车辆中电动助力转向系统的预测性故障减轻的系统及方法 (System and method for predictive fault mitigation for electric power steering systems in vehicles ) 是由 W-c·林 X·杜 B·N·西斯卡耶 于 2019-05-22 设计创作，主要内容包括：一种控制具有电动助力转向系统的车辆的方法包括产生多个可能路线。需要转向扭矩在可用扭矩范围内的所述多个可能路线中的每一者被识别为系统兼容路线。需要所述电动助力转向系统的电动马达的角位置在整个路线上的所有时间索引都在可用马达位置范围内的多个可能路线中的每一者也在被识别为系统兼容路线。所述识别的系统兼容路线中的一者基于至少一个选择标准来选择并被指定为有效路线。然后控制所述电动助力转向系统以沿所述有效路线操纵所述车辆。当所述车辆沿所述有效路线移动时,监控所述电动助力转向系统以识别其能力的劣化。(A method of controlling a vehicle having an electric power steering system includes generating a plurality of possible routes. Each of the plurality of possible routes requiring steering torque within the available torque range is identified as a system compatible route. Each of a plurality of possible routes requiring angular positions of an electric motor of the electric power steering system to be within an available range of motor positions at all time indices across the route is also being identified as a system compatible route. One of the identified system-compatible routes is selected based on at least one selection criterion and designated as a valid route. The electric power steering system is then controlled to steer the vehicle along the efficient route. Monitoring the electric power steering system to identify a degradation in its ability as the vehicle moves along the active route.)
1. A method of controlling a vehicle having an electric power steering system, the method comprising:
generating, with a computing device, a plurality of possible routes;
identifying, with the computing device, each of the plurality of possible routes that require either a steering torque within an available torque range or an angular position of an electric motor of the electric power steering system to be within an available motor position range at all time indices across the route as system compatible routes;
selecting, with the computing device, one of the identified system-compatible routes based on at least one selection criterion and designating a selected one of the system-compatible routes as a valid route; and
controlling, with the computing device, the electric power steering system to steer the vehicle along the efficient route.
2. The method of claim 1, further comprising calculating, with the computing device, an available torque from each winding of the electric motor of the electric power steering system.
3. The method of claim 2, further comprising summing, with the computing device, the available torque from each winding of the electric motor to define a total torque limit.
4. The method of claim 3, further comprising calculating, with the computing device, the steering torque for each of the plurality of possible routes from a steering system dynamics equation, wherein the steering system dynamics equation is:
wherein sign (ω) is a rotational speed of an electric motor of the electric power steering system, wherein "sign" is defined as a positive or negative value of the rotational speed (ω),is a first derivative of the rotational speed of the electric motor, J is an inertia amount in the electric power steering system, CfrIs a friction coefficient of the electric power steering system, SAT is a self-aligning torque value of the electric power steering system, and B is a damping value of the electric power steering system.
5. The method of claim 1, further comprising determining whether the angular position of the electric motor is within the range of available motor positions at all time indices throughout a possible route comprises solving, with the computing device, a first steering system position equation, a second steering position equation, and a third steering system position equation;
wherein the first steering system position equation provides the angular position of the electric motor at time index (k +1) as a function of the angular position of the electric motor at time index (k) being greater than the angular position of the electric motor at an immediately preceding time index (k-1), wherein the first steering system position equation is:
wherein θ is the electric motorAngular position, k an incremental time index, B a damping value of the electric power steering system, Δ T a discrete time period, J an amount of inertia in the electric power steering system, TExtreme limitIs the total torque limit, C, of the electric power steering systemfrIs a coefficient of friction of the electric motor, and SAT is a self-aligning torque value of the electric power steering system;
wherein the second steering system position equation provides the angular position of the electric motor at time index (k +1) in accordance with the angular position of the electric motor at time index (k) being less than the angular position of the electric motor at the immediately preceding time index (k-1), wherein the second steering system position equation is:
wherein θ is the angular position of the electric motor, k is the incremental time index, B is the damping value of the electric power steering system, Δ T is the discrete time period, J is the amount of inertia in the electric power steering system, T is the angular position of the electric motor, k is the incremental time index, B is the damping value of the electric power steering system, Δ T is the discrete time period, andextreme limitIs the total torque limit, C, of the electric power steering systemfrIs the coefficient of friction of the electric motor, and SAT is the cogging torque value of the electric power steering system;
wherein the third steering system position equation provides the angular position of the electric motor at time index (k +1) according to the angular position of the electric motor at time index (k) being equal to the angular position of the electric motor at the immediately preceding time index (k-1), and wherein the third steering system position equation is:
wherein θ is the angular position of the electric motor, k is the incremental time index, B is the damping value of the electric power steering system, and Δ t is the discrete time periodAnd J is the amount of inertia in the electric power steering system, TExtreme limitIs the total torque limit, C, of the electric power steering systemfrIs the coefficient of friction of the electric motor, and SAT is the value of the cogging torque of the electric power steering system.
6. The method of claim 1, further comprising, when none of the plurality of possible routes is identified as the system compatible route, at least one of: issuing a notification requesting vehicle maintenance, operating the vehicle with a degraded capability policy, automatically parking the vehicle, or transferring control to an operator using the computing device.
7. The method of claim 3, further comprising setting, with the computing device, a first winding counter to zero, a second winding counter to zero, and a system level fault counter to zero when the active route is specified.
8. The method of claim 7, further comprising determining, with the computing device, a torque limit from the first winding of the electric motor and a torque limit from the second winding of the electric motor as the vehicle maneuvers along the active route.
9. The method of claim 8, further comprising incrementing, with the computing device, the first winding counter by 1 when a current torque from the first winding is within a predefined torque margin for the first winding, and incrementing the second winding counter by 1 when a current torque from the second winding is within a predefined torque margin for the second winding.
10. The method of claim 9, further comprising:
comparing, with the computing device, the first winding counter to a torque counter threshold to determine whether the first winding counter is equal to or less than the torque counter threshold or whether the first winding counter is greater than the torque counter threshold; and
comparing, with the computing device, the second winding counter to the torque counter threshold to determine whether the second winding counter is equal to or less than the torque counter threshold or whether the second winding counter is greater than the torque counter threshold.
Disclosure of Invention
A method of controlling a vehicle having an electric power steering system is provided. The method includes a computing device generating a plurality of possible routes. The possible routes may include traversing the vehicle between a current location and a destination, or performing one or more maneuvers in an upcoming time interval. The computing device may also identify as a system compatible route each of a plurality of possible routes of a possible route for which variable steering torque is required to execute the possible route is within the available torque range at all time indices across the possible route. It should be appreciated that the steering torque and possibly the available torque range vary continuously in each possible route. The computing device also identifies as a system compatible route each of a plurality of possible routes that require that the variable angular position of the electric motor of the electric power steering system at all time indices across the entire route under consideration be within the available motor position range at all time indices across the entire possible route. It should be appreciated that the available electric motor position range may vary in each possible route. The computing device then selects one of the identified system-compatible routes based on at least one selection criterion and designates the selected one of the system-compatible routes as a valid route. The computing device may then control the electric power steering system of the vehicle to steer the vehicle along the effective route.
In one aspect of the method of controlling the vehicle, the computing device calculates available torque from the windings of the electric motor. Each winding may comprise a three-phase winding, which in combination with the output shaft and other windings may be considered a three-phase brushless DC motor. For example, in an electric motor having a first winding and a second winding, the calculation means calculates an available torque from the first winding of the electric motor of the electric power steering system and calculates an available torque from the second winding of the electric motor. The computing device may then sum the available torque from the first winding and the available torque from the second winding to define a total torque limit. The available torque range may be defined as a range equal to or greater than a negative value of the total torque limit and equal to or less than a positive value of the total torque limit. It should be appreciated that the negative value of the total torque limit may be considered a steering input in one of a clockwise or counterclockwise direction, and the positive value of the total torque limit may be considered a steering input in the other of the clockwise and counterclockwise direction.
In another aspect of the method of controlling the vehicle, the calculating means may calculate the available torque from the first winding and calculate the available torque from the second winding by solving torque equations for the first winding and the second winding, respectively. Each winding of the three-phase electric motor can be modeled as an equivalent DC motor. The torque equation is:
in the torque equation, TCan be usedIt is the available torque that is available,Ktis a motor constant, V, of the electric motor of the electric power steering systemBIs the voltage, V, from an energy source (e.g. a battery) powering the electric power steering systemCminIs a minimum circuit voltage of the electric power steering system below which the electric power steering system will stop operating and reset, and RCIs a resistance in the electrical circuit between the energy source and the electric power steering system. The torque equation is described in more detail in U.S. patent application No. 15/840,270, assigned to the applicant of the present application. The resistance R in the circuit between the energy source and the electric power steering system is described in more detail in U.S. patent application No. 15/333216, assigned to the applicant of the present applicationCIs estimated.
In another embodiment, the calculation means may calculate the available torque from the first winding and calculate the available torque from the second winding by solving power equations for the first winding and the second winding, respectively. The power equation is:
in the power equation, VBIs the voltage, V, from an energy source (e.g. a battery) powering the electric power steering systemCminIs a minimum circuit voltage of the electric power steering system below which the electric power steering system will stop operating and reset, RCIs a resistance, K, in the electrical circuit between the energy source and the electric power steering systemtIs a motor constant, T, of the electric motor of the electric power steering systemCan be usedIs the available torque at time index k, RMIs a resistance of the electric motor of the electric power steering system, ω is a rotational speed of the electric motor, k is the time index, and ε is a power loss of the electric power steering system that is negligible or negligible when the electric motor is operating at high efficiencyOne can make an estimate when the efficiency of the electric motor is known.
In another aspect of the method of controlling the vehicle, the computing device may calculate the steering torque for each of the plurality of possible routes according to a steering system dynamics equation. The steering system dynamics equation is:
in the steering system dynamics equation, sign (ω) is a rotation speed of an electric motor of the electric power steering system, wherein "sign" is defined as a positive value or a negative value of the rotation speed (ω),
In another aspect of the method of controlling the vehicle, the computing device may identify each of the plurality of possible routes that require variable steering torque required to execute a possible route to be within the available torque range at all time indices across the route by comparing the steering torque for each of the plurality of possible routes calculated from the steering system dynamics equation to a range between a negative value of the total torque limit and a positive value of the total torque limit. As described above, the negative value of the total torque limit may be considered a steering input in one of a clockwise or counterclockwise direction, and the positive value of the total torque limit may be considered a steering input in the other of the clockwise and counterclockwise direction. The computing device may determine that the steering torque is within the available torque range if it is determined that the required steering torque for at least one of the possible routes is equal to or greater than the negative value of the total torque limit and equal to or less than the positive value of the total torque limit.
In another aspect of the method of controlling the vehicle, the computing device may include determining whether the angular position of the electric motor at all time indices throughout the possible course is within a range of available motor positions at all time indices throughout the course includes solving a first steering system position equation, a second steering position equation, and a third steering system position equation. The first, second, and third steering system position equations may be solved to provide a range of available angular positions of the electric motor. The first steering system position equation provides the angular position of the electric motor at time index (k +1) as a function of the angular position of the electric motor at time index (k) being greater than the angular position of the electric motor at an immediately preceding time index (k-1). The first steering system position equation is:
in the first steering system position equation, θ is the angular position of the electric motor, k is an incremental time index, B is a damping value of the electric power steering system, Δ T is a discrete time period, J is an amount of inertia in the electric power steering system, TExtreme limitIs the total torque limit, C, of the electric power steering systemfrIs a friction coefficient of the electric motor, and SAT is a self-aligning torque value of the electric power steering system. The values of the variables of the first steering system position equation are considered after any gear reduction of the electric motor.
The second steering system position equation provides the angular position of the electric motor at time index (k +1) in accordance with the angular position of the electric motor at time index (k) being less than the angular position of the electric motor at the immediately preceding time index (k-1). The second steering system position equation is:
in the second steering system position equation, θ is the angular position of the electric motor, k is an incremental time index, B is the damping value of the electric power steering system, Δ T is the discrete time period, J is the amount of inertia in the electric power steering system, TExtreme limitIs the total torque limit, C, of the electric power steering systemfrIs the coefficient of friction of the electric motor, and SAT is the value of the cogging torque of the electric power steering system. The values of the variables of the second steering system position equation are considered after any gear reduction of the electric motor.
The third steering system position equation provides the angular position of the electric motor at time index (k +1) according to the angular position of the electric motor at time index (k) being equal to the angular position of the electric motor at the immediately preceding time index (k-1). The third steering system position equation is:
in the third steering system position equation, θ is the angular position of the electric motor, k is an incremental time index, B is the damping value of the electric power steering system, Δ T is the discrete time period, J is the amount of inertia in the electric power steering system, TExtreme limitIs the total torque limit, C, of the electric power steering systemfrIs the coefficient of friction of the electric motor, and SAT is the value of the cogging torque of the electric power steering system. The value of a variable of the third steering system position equation is considered after any gear reduction of the electric motor.
In one aspect of the method of controlling the vehicle, the at least one selection criterion used by the computing device to select the valid route may include, but is not limited to, at least one of estimated fuel economy and/or use of each system-compatible route, route distance of each system-compatible route, route travel time of each system-compatible route, and preferred road types encountered on each system-compatible route.
In another aspect of the method of controlling the vehicle, the computing device may issue a notification requesting vehicle maintenance when none of the plurality of possible routes is identified as the system compatible route. Additionally, the computing device may automatically park the vehicle if there is no manual manipulation of the vehicle by an operator when none of the plurality of possible routes is identified as the system compatible route.
In another aspect of the method of controlling the vehicle, the computing device may set a counter for each respective winding of the electric motor of the electric power steering system to zero once the active route is specified. For example, in an electric motor having a first winding and a second winding, the computing device may set the first winding counter to zero and may set the second winding counter to zero. Additionally, the computing device may also set a system level fault counter to zero. Then, the computing device may determine or calculate a current torque from the first winding of the electric motor and determine or calculate a current torque from the second winding of the electric motor as the vehicle maneuvers along the active route. The calculating means increments the first winding counter by 1 when the current torque output from the first winding is within a predetermined margin of a torque limit calculated for the first winding. The calculating means increments the second winding counter by 1 when the current torque output from the second winding is within a predetermined margin of a torque limit calculated for the second winding. The computing device then compares the first winding counter to a torque counter threshold to determine whether the first winding counter is equal to or less than the torque counter threshold or whether the first winding counter is greater than the torque counter threshold. Similarly, the computing device compares the second winding counter to the torque counter threshold to determine whether the second winding counter is equal to or less than the torque counter threshold or whether the second winding counter is greater than the torque counter threshold. When the first winding counter or the second winding counter is greater than the torque counter threshold, the computing device may then issue a notification requesting vehicle maintenance due to a weak or low voltage of the energy source (e.g., weak battery) or an increase in resistance in the electric power steering system.
In another aspect of the method of controlling the vehicle, the computing device may determine a current angular position of the electric motor while maneuvering the vehicle along the efficient route. The computing device increments the system-level fault counter by a value of 1 when the current angular position of the electric motor is within a predefined position margin of a position limit of the electric power steering system at the time index. The position limits of the electric power steering system may be defined by the first, second, and third steering system position equations described above. The computing device may then compare the system level fault counter to a system level fault counter threshold to determine whether the system level fault counter is equal to or less than the system level fault counter threshold or whether the system level fault counter is greater than the system level fault counter threshold. When the system-level fault counter is greater than the system-level fault counter threshold, the computing device may issue a notification requesting vehicle maintenance due to an increase in friction or resistance of the mechanical components of the steering system, an increase in resistance in the motor power circuit, or a weak power source (e.g., a weak battery).
The above method thus enables the computing device to determine whether possible routes of the vehicle are within the current capabilities of the electric power steering system, and to select the valid route, i.e. the system compatible route, from those possible routes that are within the capabilities of the electric power steering system. In addition, the above-described method enables the computing device to identify degradation in the electric power steering system as the vehicle moves along the effective route, which degradation may degrade steering capability over time. The results calculated from the first, second and third steering system position equations may be communicated to a path planning module of the computing device and used to plan future routes "on the fly" based on the limits of the electric power steering system established by the results of these equations.
The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the best modes for carrying out the present teachings when taken in connection with the accompanying drawings.
Drawings
Fig. 1 is a schematic diagram of an electric power steering system of a vehicle.
FIG. 2 is a flow chart illustrating a method of selecting an efficient route for a vehicle.
FIG. 3 is a flow chart illustrating a method of identifying a fault in an electric power steering system of a vehicle while maneuvering along an efficient route.
Detailed Description
Those of ordinary skill in the art will recognize that terms such as "above," "below," "upward," "downward," "top," "bottom," and the like are used descriptively for the figures, and do not represent limitations on the scope of the invention, as defined by the appended claims. Furthermore, the teachings may be described herein in terms of functional and/or logical block components and various processing steps. It should be appreciated that such block components may be comprised of a plurality of hardware, software, and/or firmware components configured to perform the specified functions.
Referring to the drawings, wherein like reference numbers refer to like components throughout the several views, an electric power assisted steering system is shown generally at 20 in FIG. 1. The electric power steering system 20 may be configured in any suitable manner as understood by those skilled in the art. Referring to FIG. 1, an electric power steering system 20 may include, for example, an electric motor 22 operable to apply torque to a shaft 24. The shaft 24 is connected to a steering system (not shown) of the vehicle. As understood in the art, rotation of the shaft 24 operates the steering system. The details of the steering system are not relevant to the teachings of the present invention and therefore will not be described in detail herein.
Referring to fig. 1, the electric motor 22 receives power from an energy source 26, such as, but not limited to, a battery. In the exemplary embodiment shown in fig. 1 and described herein, the electric motor 22 includes a first winding 28 and a separate second winding 30. Both the first winding 28 and the second winding 30 of the electric motor 22 are coupled to the shaft 24 and are operable to move the shaft. While the exemplary embodiments described herein relate to an electric motor 22 having a first winding 28 and a second winding 30, it should be appreciated that the teachings provided herein may be applied to systems having a motor with one or more windings. Each winding may include a three-phase winding, which in combination with the shaft 24 and other windings may be considered a three-phase brushless DC motor. The first winding 28 and the second winding 30 are independently operable and controllable to each apply torque to the shaft 24. In the exemplary embodiment shown in fig. 1 and described herein, each of the first and second windings 28, 30 receives power from the energy source 26. In other embodiments, the electric power steering assembly includes a plurality of energy sources 26 such that the first winding 28 and the second winding 30 each receive power from a respective dedicated energy source 26. The specific type and configuration of the energy source 26 is not relevant to the teachings of the present invention and will be appreciated by those skilled in the art and, therefore, will not be described in detail herein.
The electric power steering system 20 includes a first system resistor 32 and a second system resistor 34. The first system resistance 32 is a resistance in the electrical circuit between the energy source 26 and the first winding 28 of the electric motor 22. The second system resistance 34 is a resistance in the electrical circuit between the energy source 26 and the second winding 30 of the electric motor 22. The electric motor 22 includes a first electric motor resistance 36 and a second electric motor resistance 38. The first electric motor resistance 36 is a resistance in the electric motor 22 for operating the first winding 28, and the second electric motor resistance 38 is a resistance in the electric motor 22 for operating the second winding 30.
The electric power steering system 20, including the first and second windings 28, 30 of the exemplary embodiments described herein, is controlled by a computing device 40. Computing device 40 may alternatively be referred to as a controller, vehicle controller, control module, computer, autonomous driving system controller, or the like. The computing device 40 may include one or more of a variety of devices and is generally used herein to include various devices for controlling the operation of various components of the electric power steering system 20 and performing methods of controlling the electric power steering system 20 described in more detail below. For example, referring to fig. 1, a computing device 40 as used herein includes a path planning module 42, a supervisory controller 44, a first control unit 46, and a second control unit 48. The path planning module 42 may calculate different possible routes for the vehicle. The supervisory controller 44 may implement a steering control algorithm 50 for controlling the electric power steering system 20, which will be described in more detail below. The first control unit 46 and the second control unit 48 may be controlled by the supervisory controller 44 and may receive control signals therefrom. The first control unit 46 controls the operation of the first winding 28 of the electric motor 22, while the second control unit 48 controls the operation of the second winding 30 of the electric motor 22. It should be appreciated that the computing device 40 may include more or less than the exemplary devices shown in fig. 1 and described herein, and that the computing device 40 should not be limited to the particular architecture shown in fig. 1 and described herein.
The computing device 40 is operable to control operation of the electric power steering system 20. The computing device 40 may include a computer and/or processor and include software, hardware, memory, algorithms, connections, sensors, etc. for managing and controlling the operation of the electric power steering system 20. Thus, the method of controlling a vehicle having an electric power steering system 20 (described in more detail below) may be embodied as a program or algorithm operable on the computing device 40. It should be appreciated that the computing device 40 may include a device capable of analyzing data from various sensors, comparing data, making decisions required to control the operation of the electric power steering system 20, and performing the required tasks for controlling the operation of the electric power steering system 20 and performing the methods described herein.
The computing device 40 includes a tangible, non-transitory memory 52 having computer-executable instructions recorded thereon, including a steering control algorithm 50. The computing device 40 also includes a processor 54 operable to execute the steering control algorithm 50 to determine an effective route along the steering vehicle and to monitor the state of the electric power steering system 20 to ensure that the electric power steering system 20 is operating properly and is able to complete the effective route once initiated.
The computing device 40 may be embodied as one or more digital computers or hosts, each having one or more processors, Read Only Memory (ROM), Random Access Memory (RAM), Electrically Programmable Read Only Memory (EPROM), optical drive, magnetic drives, etc., a high speed clock, analog to digital conversion (A/D) circuitry, digital to analog conversion (D/A) circuitry, required input/output (I/O) circuitry, I/O devices and communication interfaces, and signal conditioning and buffer electronics.
The computer-readable memory may include a non-transitory/tangible medium that participates in providing data or computer-readable instructions. The memory may be non-volatile or volatile. Non-volatile media may include, for example, optical or magnetic disks and other persistent memory. Exemplary volatile memory may include Dynamic Random Access Memory (DRAM), which may constitute a main memory. Other examples of embodiments for memory include floppy disks, flexible or hard disks, tape or other magnetic media, CD-ROMs, DVDs, and/or other optical media, as well as other possible memory devices such as flash memory.
As described above, the processor 54 of the computing device 40 executes the steering control algorithm 50 to perform a method of controlling the vehicle, and more specifically, the electric power steering system 20 of the vehicle. Referring to fig. 2, the method includes generating a plurality of possible routes. The step of generating possible routes is generally indicated by block 102 in fig. 2. The possible routes may include traversing the vehicle between a current location and a destination, or performing one or more maneuvers in an upcoming time interval. The possible route includes a most likely desired route between a current location of the vehicle and a destination of the vehicle, or a most likely or desired maneuver in an upcoming time interval. The possible routes may be generated by the computing device 40 in a suitable manner, such as is understood by those skilled in the art. For example, the computing device 40 may use the GPS locations of the vehicle and the destination and a map saved in memory of the computing device 40 to generate a likely route that the vehicle may travel between the current location and the destination. The possible routes may include a single route or multiple routes. The particular manner in which the computing device 40 generates the possible routes is not relevant to the teachings of the present invention and is therefore not described in detail herein.
The computing device then determines whether at least one of the possible routes is a system compatible route. The step of determining whether at least one of the possible routes is a system compatible route is generally indicated by block 104 in fig. 2. The computing device 40 identifies each of a plurality of possible routes that require steering torque within all time indices (k-1, k +1, k +2,.., k + n) in the entire route to be within the available torque range at all indices (k-1, k +1, k +2,.., k + n) in the entire route or that require angular positions of the electric motor 22 of the electric power steering system 20 at all time indices on the entire route to be within the available motor positions at all time indices on the entire route as a system compatible route. The step of identifying a system compatible route is generally indicated by block 106 in fig. 2. As used herein, the term system compatible route includes possible routes that an electric power steering system is capable of performing. System compatible routes include possible routes that require the respective steering torque from the electric motor 22 to complete the respective possible route to be within the available torque range or that require the respective angular position of the electric motor 22 at all time indices throughout the route to be within the available motor position range. The system compatible route may include a plurality of possible routes. For example, in some embodiments, none of the possible routes may be identified as a system compatible route. In other embodiments, the possible routes may be identified as system compatible routes. In other embodiments, a portion of the possible routes may be identified as system compatible routes.
As described above, the computing device 40 identifies each of the possible routes for which the steering torque required to execute the respective possible route is within the available torque range of the electric power steering system 20 as a system compatible route. To this end, the computing device 40 computes a usable torque range of the electric power steering system 20. The computing device 40 calculates the available torque range by first calculating the available torque from each winding of the electric motor 22 (e.g., the first and second windings 28, 30 of the exemplary embodiments described herein), and then summing the available torque from each winding of the electric motor 22. In other words, the calculation means 40 calculates the available torque from the first winding 28 of the electric motor 22 of the electric power steering system 20 and also calculates the available torque from the second winding 30 of the electric motor 22 of the electric power steering system 20. The computing device 40 then sums the available torque from the first winding 28 and the available torque from the second winding 30 to define a total torque limit. The available torque range is a range having a lower limit equal to or greater than a negative value of the total torque limit and an upper limit equal to or less than a positive value of the total torque limit. It should be appreciated that the negative value of the total torque limit may be considered a steering input in one of a clockwise or counterclockwise direction, and the positive value of the total torque limit may be considered a steering input in the other of the clockwise and counterclockwise direction.
The available torque from the first winding 28 and the available torque from the second winding 30 may be calculated by solving a torque equation (equation 1), respectively. Each winding of the three-phase electric motor 22 can be modeled as an equivalent DC motor. The torque equation (equation 1) is defined as follows:
in the torque equation, TCan be usedIs available torque, KtIs a motor constant, V, of an electric motor 22 of the electric power steering system 20BIs a voltage, V, from an energy source 26 (e.g., a battery) that powers the electric power steering system 20CminIs the minimum circuit voltage of the electric power steering system 20 below which the electric power steering system 20 will stop operating and reset, and RCIs a resistance in the electrical circuit between the energy source 26 and the electric power steering system 20. The torque equation is described in more detail in U.S. patent application No. 15/840,270, assigned to the applicant of the present application. The resistance R in the circuit between the energy source 26 and the electric power steering system 20 is described in more detail in U.S. patent application No. 15/333,216, assigned to the applicant of the present applicationCIs estimated. It should be understood that the computing device 40 solves the torque equation for each winding of the electric motor 22. For example, in the exemplary embodiment described herein, the computing device 40 will solve the torque equation twice, once for the first winding 28 to calculate the available torque from the first winding 28, and once for the second winding 30 to calculate the available torque from the second winding 30, thereby providing a torque value for each winding of the electric motor 22. These individual torque values for each winding are then summed together to define the total torque limit for the electric motor 22. As described above, the available torque range is a range equal to or greater than the negative value of the total torque limit and equal to or less than the positive value of the total torque limit.
In another embodiment, the calculation device 40 may calculate the available torque from the first winding 28 and calculate the available torque from the second winding 30 by solving the power equations (equation 2) for the first winding 28 and the second winding 30, respectively. The power equation (equation 2) is defined as follows:
in the power equation, VBIs a voltage, V, from an energy source 26 (e.g., a battery) that powers the electric power steering system 20CminIs the minimum circuit voltage of the electric power steering system 20 below which the electric power steering system 20 will stop operating and reset, RCIs a resistance, K, in the electrical circuit between the energy source 26 and the electric power steering system 20tIs the motor constant, T, of the electric motor 22 of the electric power steering system 20Can be usedIs the available torque at time index k, RMIs the resistance of the electric motor 22 of the electric power steering system 20, ω is the rotational speed of the electric motor 22, k is the time index, and ε is the power loss of the electric power steering system 20, which can be ignored when the electric motor operates at high efficiency or estimated when the efficiency of the electric motor is known.
The computing device 40 also calculates the steering torque for each of the plurality of possible routes according to the steering system dynamics equations, which are then compared to the available torque range. The steering torque for each possible route may be calculated according to the steering system dynamics equation (equation 3). The steering system dynamics equation (equation 3) is defined as follows:
in the steering system dynamics equation, sign (ω) is the rotational speed of the electric motor 22 of the electric power steering system 20, where "sign" is defined as a positive or negative value of the rotational speed (ω),
The step of identifying each of a plurality of possible routes requiring steering torque within the available torque range includes determining whether the steering torque calculated from the steering system dynamics equations along each of the plurality of possible routes is equal to or greater than a negative value of the total torque limit and equal to or less than a positive value of the total torque limit. If the computing device 40 determines that the steering torque of the respective possible route is less than a negative value of the total torque limit, or greater than a positive value of the total torque limit, the computing device 40 does not identify the respective possible route as a system-compatible route because the respective possible route is not within the available torque range. However, if the computing device 40 determines that the steering torque for the respective possible route is equal to or greater than a negative value of the total torque limit and equal to or less than a positive value of the total torque limit, the computing device 40 does identify the respective possible route as a system-compatible route because the respective possible route is within the available torque range. The computing device 40 compares the steering torque for each respective possible route to the available torque range to determine whether the respective possible route is within the available torque range, and thus, whether the route is system compatible.
As described above, each of the possible routes may be identified as a system compatible route if the steering torque along the respective possible route is within the available torque range. Additionally, as described above, each of the possible routes may be identified as a system compatible route if the angular positions of the electric motor 22 at all time indices in the route are within the available motor position range. The computing device 40 may determine whether the angular position of the electric motor 22 at all time indices across the entire route is within the range of available motor positions for each of the plurality of possible routes by solving a first steering system position equation (equation 4), a second steering position equation (equation 5), and a third steering system position equation (equation 6) described in detail below.
The first steering system position equation (equation 4) provides the angular position of the electric motor 22 at the time index (k +1) based on the angular position of the electric motor 22 at the time index (k) being greater than the angular position of the electric motor 22 at the immediately preceding time index (k-1). The first steering system position equation (equation 4) is defined as follows:
in the first steering position equation (equation 4), θ is the angular position of the electric motor 22, k is the incremental time index, B is the damping value of the electric power steering system 20, Δ T is the discrete time period, J is the amount of inertia in the electric power steering system 20, TExtreme limitIs the total torque limit, C, of the electric power steering system 20frIs the coefficient of friction of the electric motor 22, and SAT is the value of the cogging torque of the electric power steering system 20. The values of the variables of the first steering system position equation are considered after any gear reduction of the electric motor.
The second steering system position equation (equation 5) provides the angular position of the electric motor 22 at time index (k +1) based on the angular position of the electric motor 22 at time index (k) being less than the angular position of the electric motor 22 at the immediately preceding time index (k-1). The second steering system position equation (equation 5) is defined as follows:
in the second steering system position equation (equation 5), θ is the angular position of the electric motor 22, k is an incremental time index, B is the damping value of the electric power steering system 20, and Δ t is departureA dispersion period, J, is an amount of inertia in the electric power steering system 20, TExtreme limitIs the total torque limit, C, of the electric power steering system 20frIs the coefficient of friction of the electric motor 22, and SAT is the value of the cogging torque of the electric power steering system 20. The values of the variables of the second steering system position equation are considered after any gear reduction of the electric motor.
The third steering system position equation (equation 6) provides the angular position of the electric motor 22 at time index (k +1) which is equal to the angular position of the electric motor 22 at the immediately preceding time index (k-1). The third steering system position equation (equation 6) is defined as follows:
in the third steering system position equation (equation 6), θ is the angular position of the electric motor 22, k is an incremental time index, B is the damping value of the electric power steering system 20, Δ T is a discrete time period, J is an inertia amount in the electric power steering system 20, TExtreme limitIs the total torque limit, C, of the electric power steering system 20frIs the coefficient of friction of the electric motor 22, and SAT is the value of the cogging torque of the electric power steering system 20. The value of a variable of the third steering system position equation is considered after any gear reduction of the electric motor.
If the angular position of the electric motor 22 for the respective possible route satisfies each of the first, second, and third steering system position equations (equation 4, 5, 6) for all time indices of the entire possible route, the computing device 40 identifies the respective possible route as a system compatible route. However, if the angular position of the electric motor 22 for the respective possible route fails to satisfy each of the first, second, and third steering system position equations (equation 4, 5, 6) for at least one of the time indices of the entire respective possible route, the computing device 40 does not identify the respective route as a system-compatible route.
If computing device 40 is unable to identify at least one of the possible route identifications as a system-compatible route, i.e., there is no system-compatible route, computing device 40 may issue a notification requesting vehicle maintenance. The step of issuing a notification that no possible route is a system compatible route is generally indicated by block 108 in fig. 2. The computing device 40 may issue the notification in a suitable manner, such as, but not limited to, flashing a warning light, displaying a message to an occupant of the vehicle, transmitting a communication to a remote location, and the like. Additionally, when no possible route is identified as a system compatible route, the computing device 40 may automatically park the vehicle in the appropriate location or transfer control of the vehicle to the operator.
Once computing device 40 identifies system-compatible routes, computing device 40 may select one of the identified system-compatible routes and designate the selected one of the system-compatible routes as the active route. The step of selecting an active route is generally indicated by block 110 in fig. 2. The computing device 40 may select an active route from the identified system-compatible routes based on at least one predefined selection criterion. The selection criteria may include, but are not limited to, at least one of an estimated highest fuel economy of the vehicle available from the respective system-compatible route, a shortest respective route distance available from the respective system-compatible route, a shortest route travel time available from the respective system-compatible route, and a preferred road type traversed along the respective system-compatible route. It should be appreciated that the selection of an efficient route may be based on multiple selection criteria, and the importance of different selection criteria may be weighted to favor one criterion over another.
Once the active route is selected, the computing device 40 may control the electric power steering system 20 of the vehicle to steer the vehicle along the active route. The step of maneuvering the vehicle along the efficient route is generally indicated by block 112 in FIG. 2. It should be appreciated that computing device 40 may also control other vehicle systems to move the vehicle along the efficient route, including but not limited to, a powertrain system, a braking system, a navigation system, and the like. The manner in which the computing device 40 controls the electric power steering system 20 to move the vehicle along an efficient path is understood by those skilled in the art to be irrelevant to the teachings of the present invention and therefore will not be described in detail herein.
The above method may be implemented to select an effective route that the electric power steering system 20 can perform. Additional steps may be implemented to monitor the state of the electric power steering system 20 as the vehicle travels along the selected active route, and take corrective action if necessary.
Referring to fig. 3, when an active route is specified or generated instantaneously by the path planning module 42, the method may further include the computing device 40 setting a winding counter for each winding of the electric motor 22 to zero. For example, in the exemplary embodiment described herein, where the electric motor 22 includes the first and second windings 28, 30, the computing device 40 sets the first winding counter to zero and the second winding counter to zero. In addition, the computing device 40 sets the system level fault counter to zero. The step of setting the winding counter and the system level fault counter to zero is generally indicated by block 130 in fig. 3. The first winding counter, the second winding counter, and the system level fault counter are counters, i.e., values, stored in the memory 52 of the computing device 40. Each of the first winding counter, the second winding counter, and the system level fault counter may be incremented as described below to track the condition of the electric power steering system 20. While the exemplary embodiments described herein describe a first winding counter and a second winding counter, it should be appreciated that if the electric motor 22 of the electric power steering system 20 includes more than the exemplary two windings, the computing device 40 will track a corresponding number of winding counters. For example, if the electric motor 22 is configured to include three windings, the computing device 40 will store and track three winding counters, i.e., a respective winding counter for each winding of the electric motor 22.
For each incremental time index (k) when maneuvering the vehicle along the active route, the computing device 40 determines a torque limit for each respective winding of the electric motor. The step of calculating the torque limit for each respective winding of the electric motor is generally indicated by block 132 in fig. 3. Thus, the calculation means 40 calculates the torque limit of the first winding 28 of the electric motor 22 and the torque limit of the second winding 30 of the electric motor 22. For example, the torque limit for each respective winding may be calculated from equation 1 or 2 above.
For each incremental time index (k), the computing device 40 then controls the electric power steering system 20 such that the torque output from each winding is less than its respective torque limit calculated in block 132. The steps of controlling the electric power steering system 20 are generally indicated by block 133 in fig. 3. It should be appreciated that the computing device 40 controls the electric power steering system to follow an efficient route. The valid routes may include selected ones of the compatible routes, or may alternatively include routes generated on the fly.
To control the power steering system 20 within the calculated torque limits of the respective windings, the computing device 40 may calculate the current or output torque of each of the windings in a suitable manner. For example, the current or output torque of each of the windings may be calculated according to the torque equation T ═ KI, where T is the current torque from the windings, K is the motor constant of the equivalent DC motor, and I is the motor current of the equivalent DC motor. Alternatively, one or more sensors and associated algorithms may be used to measure and/or sense the current or output torque of each of the windings. The current or output torque of each winding of electric motor 22 may be calculated and/or determined in some other manner not specifically described herein.
The computing device 40 increments the first winding counter by 1 when the currently available torque at the corresponding time index (k) from the first winding 28 is within the predetermined torque margin for the first winding 28. The predefined torque margin may include a value, coefficient, percentage, or range of torque limits for each respective winding. The torque margin establishes a range having a lower end slightly less than the total torque limit and an upper end equal to the total torque limit. The torque margin may take into account the absolute value of the current torque, or may include positive and negative ranges of positive and negative torque values, respectively. Similarly, the calculating means 40 increments the second winding counter by a value of 1 when the currently available torque at the respective time index (k) from the second winding 30 is within the predefined torque margin for the second winding 30. The computing device 40 increments the first winding counter and the second winding counter for each occurrence, wherein the currently available torque at the respective time index (k) from the respective winding is within the predefined torque margin for the respective winding. The step of incrementing the winding counter is generally indicated by block 134 in fig. 3.
The computing device 40 then compares the first winding counter to the torque counter threshold to determine whether the first winding counter is equal to or less than the torque counter threshold or whether the first winding counter is greater than the torque counter threshold. Similarly, the computing device 40 compares the second winding counter to the torque counter threshold to determine whether the second winding counter is equal to or less than the torque counter threshold or whether the second winding counter is greater than the torque counter threshold. The step of determining whether the respective winding counter is greater than the torque counter threshold is generally indicated by block 136 in fig. 3. When the first winding counter or the second winding counter is greater than the torque counter threshold (indicated generally at 138), the computing device 40 may issue a notification requesting vehicle maintenance due to a weak or low voltage from the energy source 26 or an increase in resistance in the electric power steering system 20. The step of issuing a notification of vehicle maintenance due to a voltage drop or resistance increase is generally indicated by block 140 in fig. 3. The computing device 40 may issue the notification in a suitable manner, such as, but not limited to, flashing a warning light, displaying a message to an occupant of the vehicle, transmitting a communication to a remote location, and the like. Additionally, when the first winding time counter or the second winding counter is greater than the torque counter threshold, the computing device 40 may control the electric power steering system 20 using the degraded capability strategy, automatically park the vehicle in a suitable location, or may transfer control of the vehicle to an operator.
When the current torque from the electric motor 22 approaches the total torque limit, the electric motor 22 is indicated to be approaching its torque capacity, and further degradation may prevent the electric motor 22 from being able to provide the required torque for maneuvering the vehicle along the efficient route. The number of occurrences in which the current torque of one of the windings of the electric motor 22 is within the torque margin is tracked via their respective winding counters to identify which winding may be faulty. As the value of each respective winding counter increases, the likelihood of a winding failure increases. The torque counter threshold is set to a level indicating a possible fault.
Additionally, the computing device 40 determines a current angular position of the electric motor 22 at the current time index (k) as the vehicle maneuvers along the efficient route. The step of calculating the current angular position of the electric motor 22 along the active route is generally indicated by block 142 in fig. 3. When the current angular position of the electric motor 22 at the current time index (k) is within the predefined position margin of the position limits of the electric power steering system 20, the calculation means 40 increments the system-level fault counter by a value of 1. The step of incrementing the system level fault counter is generally indicated by block 144 in fig. 3. The position limit of the electric power steering system 20 at the time index (k +1) may be defined or calculated using the above-described first steering system position equation (equation 4), second steering position equation (equation 5), and third steering system position equation (equation 6). The calculation means 40 calculates the position limit of the electric power steering system 20 at the time index (k +1) using the information available from the position limit at the time index (k). The position margin may include a value, coefficient, percentage, or range of position limits. The position margin establishes a range having a lower end slightly less than the position limit and an upper end equal to the position limit. The position margin may include positive and negative ranges for positive and negative position values, respectively. The positive position value may be associated with either the clockwise steering input or the counterclockwise steering input, and the negative position value may be associated with the other of the clockwise steering input and the counterclockwise steering input. When the current angular position of the electric motor 22 at the respective time index (k) is within the predefined position margin of the position limit, the calculation means 40 increments the system level fault counter by 1. The computing device 40 increments a system level fault counter for each occurrence, wherein the current angular position of the electric motor 22 at the respective time index (k) is within a predefined position margin.
Computing device 40 may then compare the system level fault counter to the system level fault counter threshold to determine whether the system level fault counter is equal to or less than the system level fault counter threshold or whether the system level fault counter is greater than the system level fault counter threshold. The step of determining whether the system level fault counter is greater than the system level fault counter threshold is indicated generally by block 146 in FIG. 3. When the system-level fault counter is greater than the system-level fault counter threshold (generally indicated at 148), the computing device 40 may issue a notification requesting vehicle maintenance due to increased friction and/or drag in mechanical components of the steering system, increased resistance in the motor power circuit, or a weak power source (e.g., a weak battery). The step of issuing a notification due to an increase in resistance in the mechanical components of the steering system is generally indicated by block 150 in fig. 3. The computing device 40 may issue the notification in a suitable manner, such as, but not limited to, flashing a warning light, displaying a message to an occupant of the vehicle, transmitting a communication to a remote location, and the like. Additionally, when the system-level fault counter is greater than the system-level counter threshold, the computing device 40 may control the electric power steering system 20 using the degraded-capability strategy, automatically park the vehicle in the appropriate location, or may transfer control of the vehicle to an operator.
When the current angular position of the electric motor 22 at time index (k) approaches the position limit, it is indicated that the electric motor 22 is approaching its travel limit, and further degradation may prevent the electric motor 22 from being able to provide the required movement for maneuvering the vehicle along the efficient route. The number of occurrences of the current angular position of the electric motor 22 within the position margin is tracked via a system-level fault counter. As the value of the system level fault counter increases, the likelihood of a fault in the electric power steering system 20 increases. The system level fault counter threshold is set to a level indicating a possible fault.
Additionally, the results calculated from the first, second, and third steering system position equations (equation 4, 5, 6) may be communicated to the path planning module 42 of the computing device 40 and used to "on the fly" plan a future route for the next time interval (k +1) based on the limits of the electric power steering system 20 established by the results of these steering position equations. To this end, the path planning module 42 may plan future routes and/or vehicle maneuvers based on the current operating capabilities of the electric power steering system 20. The step of communicating the results calculated from the steering system position equation to the path planning module is generally indicated by block 152 in fig. 3.
The detailed description and drawings or figures support and describe the invention, but the scope of the invention is defined only by the claims. While certain best modes and other embodiments for carrying out the present teachings have been described in detail, various alternative designs and embodiments for practicing the invention are also presented.
- 上一篇：一种医用注射器针头装配设备
- 下一篇：转向系统