阅读说明：本技术 提高蜗轮耐久性的可变行程停止件 (Variable stroke stop for improving durability of worm gear ) 是由 M·J·纳基尔斯基 J·弗兰尼亚斯 K·乔杜尔 于 2021-03-29 设计创作，主要内容包括：描述了使用控制器控制马达运行的技术方案：使马达通电,以旋转驱动轴和蜗杆；通过蜗杆驱动蜗轮；响应于蜗轮旋转至多个第一停止位置中的给定的一个,使马达停止旋转驱动轴；以及,将第一停止位置中的给定的一个改变为第一停止位置中的另一个。一种用于控制机器的方法包括：通过马达旋转驱动轴；通过蜗杆驱动蜗轮,以使蜗轮旋转；响应于蜗轮旋转至多个第一停止位置中的给定的一个,使马达停止旋转驱动轴；以及,将第一停止位置中的给定的一个改变为第一停止位置中的另一个。(The technical scheme of controlling the motor to run by using the controller is described as follows: energizing the motor to rotate the drive shaft and the worm; the worm drives the worm wheel; stopping the motor from rotating the drive shaft in response to the worm gear rotating to a given one of the plurality of first stop positions; and changing a given one of the first stop positions to another one of the first stop positions. A method for controlling a machine comprising: rotating a drive shaft by a motor; driving the worm gear through the worm to rotate the worm gear; stopping the motor from rotating the drive shaft in response to the worm gear rotating to a given one of the plurality of first stop positions; and changing a given one of the first stop positions to another one of the first stop positions.)

1. A control system for controlling operation of a motor, comprising:

a processor; and

a memory comprising instructions that, when executed by the processor, cause the processor to:

energizing the motor to rotate a drive shaft;

driving a worm wheel through a worm coupled with the driving shaft to rotate the worm wheel in a first direction;

stopping the motor from rotating the drive shaft in response to the worm gear rotating in the first direction to a given one of a plurality of first stop positions; and the number of the first and second groups,

changing a given one of the plurality of first stop positions to another one of the plurality of first stop positions.

2. The control system of claim 1, wherein the instructions, when executed by the processor, further cause the processor to:

driving the worm gear via the worm to rotate the worm gear in a second direction opposite the first direction;

stopping the motor from rotating the drive shaft in response to the worm gear rotating in the second direction to a given one of a plurality of second stop positions; and the number of the first and second groups,

changing a given one of the plurality of second stop positions to another one of the plurality of second stop positions.

3. The control system of claim 1, wherein the plurality of first stop positions correspond to different gear teeth on the worm gear, respectively.

4. The control system of claim 1, wherein adjacent ones of the first plurality of stop positions are spaced from one or more gear teeth of the worm gear.

5. The control system of claim 1, wherein adjacent ones of the first plurality of stop positions are spaced from one another by two or more gear teeth of the worm gear.

6. The control system of claim 1, wherein the plurality of first stop positions includes three different first stop positions.

7. The control system of claim 1, wherein a given one of the first plurality of stop positions is changed to another one of the first plurality of stop positions each time the worm gear is driven away from the given one of the first plurality of stop positions.

8. The control system of claim 1, wherein changing the given one of the plurality of first stop positions to another one of the plurality of first stop positions comprises changing the given one of the plurality of first stop positions in a predetermined pattern.

9. The control system of claim 1, wherein the motor is configured to perform at least one of: applying an assist torque to a steering system of a vehicle, and controlling the steering system.

10. A method for controlling a machine, the method comprising:

rotating a drive shaft by a motor;

driving a worm wheel through a worm coupled with the driving shaft to rotate the worm wheel in a first direction;

stopping the motor from rotating the drive shaft in response to the worm gear rotating in the first direction to a given one of a plurality of first stop positions; and

changing a given one of the plurality of first stop positions to another one of the plurality of first stop positions.

11. The method of claim 10, further comprising:

driving the worm gear via the worm to rotate the worm gear in a second direction opposite the first direction;

stopping the motor from rotating the drive shaft in response to the worm gear rotating in the second direction to a given one of a plurality of second stop positions; and the number of the first and second groups,

changing a given one of the plurality of second stop positions to another one of the plurality of second stop positions.

12. The method of claim 10, wherein adjacent ones of the first plurality of stop positions are spaced from one another by one gear tooth of the worm gear.

13. The method of claim 10, wherein adjacent ones of the plurality of first stop positions are spaced from each other by an amount between one and two gear teeth of the worm gear.

14. The method of claim 10, wherein adjacent ones of the first plurality of stop positions are spaced from one another by two or more gear teeth of the worm gear.

15. The method of claim 10, wherein adjacent ones of the plurality of second stop positions are spaced from each other by an amount between one and two gear teeth of the worm gear.

16. The method of claim 10, wherein the given one of the plurality of first stop positions is changed to another one of the plurality of first stop positions each time the worm gear is driven off the given one of the plurality of first stop positions.

17. The method of claim 10, wherein changing the given one of the plurality of first stop positions to another one of the plurality of first stop positions comprises changing the given one of the plurality of first stop positions in a predetermined pattern.

18. The method of claim 10, wherein the machine is configured to perform at least one of: applying an assist torque to a steering system of a vehicle, and controlling the steering system.

19. A method for controlling a power steering system in a vehicle, the method comprising:

rotating a drive shaft by a motor;

driving a worm wheel through a worm coupled with the driving shaft to rotate the worm wheel in a first direction;

stopping the motor from rotating the drive shaft in response to the worm gear rotating in the first direction to a given one of a plurality of first stop positions; and the number of the first and second groups,

changing a given one of the plurality of first stop positions to another one of the plurality of first stop positions.

20. The method of claim 19, further comprising:

driving the worm gear via the worm to rotate the worm gear in a second direction opposite the first direction;

stopping the motor from rotating the drive shaft in response to the worm gear rotating in the second direction to a given one of a plurality of second stop positions; and the number of the first and second groups,

changing a given one of the plurality of second stop positions to another one of the plurality of second stop positions.

Background

The present application relates generally to methods and systems for machines including worm gears, and more particularly to methods and systems for controlling a motor to stop a worm gear at a predetermined stop position.

Many different machines and machine components include controllers that control motors to drive loads using worm gears. One example of a machine having such a configuration is in an Electric Power Steering (EPS) system of a motor vehicle.

Worm gear durability depends on the highest load applied to the worm gear, which is typically applied when the worm gear is in the end of travel (EOT) position. The worm gear endurance fatigue limit is related to loading one or more teeth of the worm gear at each of two EOT positions corresponding to the worm gear being driven in each of two opposite directions (e.g., clockwise and counterclockwise).

Disclosure of Invention

According to one or more embodiments, a control system for controlling operation of a motor includes: a processor; and a memory including instructions that, when executed by the processor, cause the processor to: energizing the motor to rotate the drive shaft; driving a worm wheel through a worm coupled with the driving shaft to rotate the worm wheel in a first direction; stopping the motor from rotating the drive shaft in response to the worm gear rotating in the first direction to a given one of the plurality of first stop positions; and changing a given one of the plurality of first stop positions to another one of the plurality of first stop positions.

According to one or more embodiments, a method for controlling a motor includes: rotating a drive shaft by a motor; driving a worm wheel through a worm coupled with the driving shaft to rotate the worm wheel in a first direction; stopping the motor from rotating the drive shaft in response to the worm gear rotating in the first direction to a given one of the plurality of first stop positions; and changing a given one of the first stop positions to another one of the first stop positions.

According to one or more embodiments, a method for controlling a power steering system in a vehicle comprises the steps of: rotating a drive shaft by a motor; driving a worm wheel through a worm coupled with the driving shaft to rotate the worm wheel in a first direction; stopping the motor from rotating the drive shaft in response to the worm gear rotating in the first direction to a given one of the plurality of first stop positions; and changing a given one of the plurality of first stop positions to another one of the plurality of first stop positions.

These and other advantages and features will become apparent from the following description taken in conjunction with the accompanying drawings.

Drawings

The subject matter regarded as the disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The above and other features and advantages of the present disclosure will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 depicts a block diagram of an exemplary embodiment of an electric power steering system in accordance with aspects of the present disclosure;

FIG. 2 depicts a worm engaged with a worm gear in accordance with aspects of the present disclosure;

FIG. 3 depicts a gear set including a worm and a worm gear in accordance with aspects of the present disclosure; and

FIG. 4 depicts the gear set of FIG. 3 having a plurality of first stop positions and a plurality of second stop positions.

Detailed Description

Reference will now be made to the accompanying drawings, in which the disclosure will be described with reference to specific embodiments, but is not limited thereto. It is to be understood that the disclosed embodiments are merely illustrative of the present disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale, some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

As used herein, the terms "module" and "sub-module" refer to one or more processing circuits, such as an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. It is understood that the sub-modules described below may be combined and/or further partitioned.

Reference will now be made to the accompanying drawings in which the technical solutions will be described with reference to specific embodiments, but without being limited thereto. FIG. 1 is an exemplary embodiment of an electric power steering system (EPS)40 suitable for implementing the disclosed embodiments. The steering mechanism 36 is a rack-and-pinion type system, and includes a rack (not shown) located within the housing 50 and a pinion (also not shown) located below the gear box 52. When an operator input member (hereinafter referred to as a steering wheel 26 (e.g., a hand wheel, etc.)) is rotated, the upper steering shaft 29 is rotated, and the lower steering shaft 51 connected to the upper steering shaft 29 through the universal joint 34 rotates the pinion. Rotation of the pinion gear moves a rack that moves tie rods (tie rod)38 (only one shown) and, in turn, knuckles 39 (only one shown), which knuckles 39 turn one or more steerable wheels 44 (only one shown).

The electric power steering assist is provided by a control device, generally indicated by reference numeral 24, and includes a controller 16 and an electric machine (electric machine)19, the electric machine 19 may be a Permanent Magnet Synchronous Motor (PMSM), hereinafter referred to as the electric machine 19. The controller 16 is powered by the vehicle power supply 10 via line 12. The controller 16 receives a vehicle speed signal 14 from a vehicle speed sensor 17 that is representative of the vehicle speed. The steering angle is measured by a position sensor 32, which may be an optically encoded type sensor, a variable resistance type sensor, or any other suitable type of position sensor, and provides a position signal 20 to the controller 16. The motor speed may be measured using a tachometer (tachmeter) or any other device and transmitted as a motor speed signal 21 to the controller 16. The motor speed, in ω m, can be measured, calculated, or a combination of the two. For example, the motor speed ω m may be calculated as a change in the motor position θ measured by the position sensor 32 over a prescribed time interval. For example, the motor speed ω m may be determined as a derivative of the motor position θ according to the formula ω m ═ Δ θ/Δ t, where Δ t is the sampling time and Δ θ is the change in position during the sampling interval. Alternatively, the motor speed may be derived from the motor position as a rate of change of position with respect to time. It will be appreciated that there are many well known methods to calculate the derivative function.

When the steering wheel 26 is turned, the torque sensor 28 senses the torque applied to the steering wheel 26 by the vehicle operator. The torque sensor 28 may include a torsion bar (not shown) and a variable resistance type sensor (also not shown) that outputs a variable torque signal 18 to the controller 16 related to the amount of torsion on the torsion bar. Although this is one type of torque sensor, any other suitable torque sensing device used with known signal processing techniques is sufficient. In response to the various inputs, the controller sends a command 22 to the electric motor 19, which provides torque assistance to the steering system through the worm 47 and worm gear 48, thereby providing torque assistance for vehicle steering.

It should be noted that although the disclosed embodiments are described with reference to motor control for electric power steering applications, it will be understood that these references are merely illustrative and that the disclosed embodiments may be applied to any motor control application that uses an electric motor, e.g., steering, valve control, etc. Further, references and descriptions herein may be applicable to various forms of parameter sensors, including but not limited to torque, position, speed, and the like. It should also be noted that the electric machine referred to herein includes, but is not limited to, a motor, to which reference will be made hereinafter for the sake of brevity.

In the depicted control system 24, the controller 16 utilizes torque, position, and speed, among other things, to calculate one or more commands to deliver the desired output power. The controller 16 is provided in communication with sensors and various systems of the motor control system. The controller 16 receives signals from each of the system sensors, quantifies the received information, and provides (in this case, for example, to the motor 19) one or more output command signals responsive thereto. The controller 16 is configured to generate a corresponding one or more voltages from an inverter (not shown), which may optionally be integrated with the controller 16 and referred to herein as the controller 16, such that when the one or more voltages are applied to the motor 19, a desired torque or position is generated. In one or more examples, controller 16 operates as a current regulator in a feedback control mode to generate command 22. Alternatively, in one or more examples, controller 16 operates in a feed-forward control mode to generate command 22. Since these voltages are related to the position and speed of the motor 19 and the desired torque, the position and/or speed of the rotor and the torque applied by the operator are determined. A position encoder is connected to the lower steering shaft 51 or at an end of the motor 19 to detect the angular position θ. The encoder may sense the rotational position based on optical detection, magnetic field changes, or other methods. Typical position sensors include potentiometers (potentiometers), resolvers (resolvers), synchronizers (synchronizers), encoders, and the like, as well as combinations comprising at least one of the foregoing. The position encoder outputs a position signal 20 that is indicative of the angular position of the lower steering shaft 51, and thus of the motor 19.

The desired torque may be determined by one or more torque sensors 28 that transmit a torque signal 18 indicative of the applied torque. One or more exemplary embodiments include such a torque sensor 28 and one or more torque signals 18 therefrom, as may be responsive to a compliant torsion bar, a T-bar, a spring, or similar device (not shown) configured to provide a response indicative of an applied torque.

In one or more examples, one or more temperature sensors 23 are located at the motor 19. Preferably, the temperature sensor 23 is configured to directly measure the temperature of the sensing portion of the motor 19. The temperature sensor 23 transmits a temperature signal 25 to the controller 16 to assist in the processing and compensation specified herein. Typical temperature sensors include thermocouples, thermistors, thermostatic controls, and the like, as well as combinations comprising at least one of the foregoing sensors, which when properly positioned, provide a calibratable signal proportional to a particular temperature.

The position signal 20, the velocity signal 21, and the one or more torque signals 18, etc. are applied to the controller 16. The controller 16 processes all of the input signals to generate values corresponding to each of these signals to produce rotor position values, motor speed values, and torque values, which may be used for processing in the algorithms specified herein. Measurement signals such as those described above are also typically linearized, compensated, and filtered as necessary to enhance characteristics or eliminate undesirable characteristics in the acquired signals. For example, the signal may be linearized to increase processing speed, or to account for a larger dynamic range of the signal. In addition, frequency-based or time-based compensation and filtering may be used to eliminate noise or avoid undesirable spectral characteristics.

To perform the prescribed functions and desired processing, and calculations performed thereby (e.g., identification of motor parameters, one or more control algorithms, etc.), the controller 16 may include, but is not limited to, one or more processors, one or more computers, one or more DSPs, memory, storage (storage), one or more registers, timers, one or more interrupts (interrupts), one or more communication interfaces, and input/output signal interfaces, etc., as well as combinations comprising at least one of the foregoing. For example, the controller 16 may include input signal processing and filtering to enable accurate sampling and conversion or acquisition of such signals from the communication interface. Additional features of the controller 16 and some of the processes therein will be discussed thoroughly later in this document.

Fig. 2 shows a worm 47 in mesh with a worm wheel 48. Specifically, fig. 2 shows a drive shaft 60 coupled with the worm 47, wherein the worm 47 includes helical gear teeth 62 extending helically around the drive shaft 62. Fig. 2 also shows helical gear teeth 62 of worm 47, which mesh with three gear teeth 70 of worm wheel 48. It should be appreciated that the helical gear teeth 62 of the worm 47 may have other sizes or shapes that may mesh with more or less than three gear teeth 70 of the worm gear 48. In operation, the controller 16 energizes the motor 19 (not shown in fig. 2) causing the drive shaft 60 to rotate about the axis a, thereby causing the worm 47 to rotate. Rotation of the worm 47 drives rotation of the worm gear 48. It should be understood that the worm gear 48 may be driven in either of two opposite directions. For example, the worm wheel 48 may be driven to rotate in either a Clockwise (CW) direction or a counterclockwise (CCW) direction by driving the motor 19 and the worm 47 in either of two opposite directions.

Fig. 3 shows a gear set including a worm 47 and a worm gear 48 in accordance with aspects of the present disclosure. The gear sets provided may be used in any of a number of different machines or machine applications. For example, the gear set provided may be used in an electric power steering system (EPS) 40. The drive shaft 60 includes a connection 64, such as a splined area, for connection to the motor 19.

The first stop position 80 is shown as a radial line superimposed on the worm gear 48. The first stop position 80 represents an end of travel (EOT) rotational position of the worm gear 48 when the worm gear 48 is moving in a first direction (e.g., clockwise). The second stop position 82 is shown as a radial line superimposed on the worm gear 48. The second stop position 82 represents an end of travel (EOT) rotational position of the worm gear 48 when the worm gear 48 is moving in a second direction (e.g., counterclockwise) opposite the first direction. The stop positions 80, 82 may represent positions where the worm gear 48 must stop to prevent over-travel of the steering system and/or stress system components, which may be caused by torque applied by the motor 19 to mechanical stops that limit system travel. The worm gear 48 can experience the highest torque loads at or near the stop positions 80, 82. This is related to the maximum force required to move the wheel at the EOT position. The steering rack force generated when parking, including the force transmitted to the worm gear 48, is critical to sizing the steering system. The total displacement force of the rack is the sum of the left pull rod force and the right pull rod force. The main effects of the rack force level at parking are axle kinematics, front axle load, tire size, air pressure in the tires, and the friction value of the road surface.

In the example configuration, the controller 16 energizes the motor 19 to rotate the drive shaft 60, which turns the worm 47. Then, the worm 47 drives the worm wheel 48, so that the worm wheel 48 rotates. In response to the worm gear rotating to a respective one of the stop positions 80, 82, the controller 16 may cause the motor 19 to stop rotating the drive shaft 60, thereby stopping driving the worm gear 48. For example, once the worm gear 48 rotates to or beyond the first stop position 80, the motor 19 may stop driving the worm gear 48 in the first direction. Similarly, once the worm gear 48 rotates to or beyond the second stop position 82, the motor 19 may stop driving the worm gear 48 in the second direction.

Fig. 4 depicts the gear set of fig. 3 having a plurality of first stop positions 80a, 80b, 80c and a plurality of second stop positions 82a, 82b, 82 c. Specifically, fig. 4 shows a gear set of the present disclosure that includes three first stop positions 80a, 80b, 80c and three second stop positions 82a, 82b, 82 c. However, the plurality of first stop positions may include any number of two or more first stop positions and the plurality of second stop positions may include any number of two or more second stop positions.

The first stop positions 80a, 80b, 80c may be angularly spaced from one another by any amount. In some embodiments, the first stop positions 80a, 80b, 80c each correspond to a different gear tooth 70 of the worm gear 48. In one example embodiment, the first stop positions 80a, 80b, 80c are spaced from one another by one or more gear teeth 70 of the worm gear 48. In some embodiments, the first stop positions 80a, 80b, 80c are spaced from one another by two or more gear teeth 70 of the worm gear 48. As shown in FIG. 2, since the worm 47 can interact mechanically with two or more of the gear teeth 70 of the worm gear 48 at any given time, it is advantageous to spread the wear on the worm gear 48 to space the first stop positions 80a, 80b, 80c a greater amount. For example, one gear tooth 70 may be in meshing engagement with the worm 47 at two different first stop positions 80a, 80b, 80c that are spaced from one gear tooth 70 of the worm gear 48, but the same gear tooth 70 may not be in meshing engagement with the worm 47 at two different first stop positions 80a, 80b, 80c that are spaced from one another by two gear teeth 70 of the worm gear 48.

The second stop positions 82a, 82b, 82c may be angularly spaced from one another by any amount. In some embodiments, the second stop positions 82a, 82b, 82c each correspond to a different gear tooth 70 of the worm gear 48. In one example embodiment, the second stop positions 82a, 82b, 82c are spaced from one another by one or more gear teeth 70 of the worm gear 48. In some embodiments, the second stop positions 82a, 82b, 82c are spaced from one another by two or more gear teeth 70 of the worm gear 48. As shown in FIG. 2, since the worm 47 can interact mechanically with two or more of the gear teeth 70 of the worm gear 48 at any given time, it is advantageous to spread wear on the worm gear 48 to space the second stop positions 82a, 82b, 82c a greater amount. For example, one gear tooth 70 may engage the worm 47 at two different second stop positions 82a, 82b, 82c that are spaced from one gear tooth 70 of the worm gear 48, but the same gear tooth 70 may not engage the worm 47 at two different second stop positions 82a, 82b, 82c that are spaced from two gear teeth 70 of the worm gear 48.

The system may be configured to rotate or alternate between different ones of the first stop positions 80a, 80b, 80c and/or different ones of the second stop positions 82a, 82b, 82 c. In some embodiments, the system is configured to change to a different one of the first stop positions 80a, 80b, 80c each time the worm gear is driven away from the first stop positions 80a, 80b, 80 c. For example, a given one of the first stop positions 80a, 80b, 80c for stopping the worm gear 48 may be changed each time the worm gear 48 is rotated past all of the first stop positions 80a, 80b, 80c (i.e., toward the second stop positions 82a, 82b, 82 c). Alternatively, a given one of the first stop positions 80a, 80b, 80c for stopping the worm wheel 48 may be changed each time the worm wheel 48 is rotated beyond some other predetermined position. In some embodiments, changing a given one of the first stop positions 80a, 80b, 80c for stopping the worm gear 48 to another one of the first stop positions 80a, 80b, 80c includes changing the given one of the first stop positions 80a, 80b, 80c in a predetermined pattern. For example, the stop position may be rotated in a repeating pattern (e.g., a, b, c …, or a, b, a, b …).

Similarly, the system may be configured to change to a different one of the second stop positions 82a, 82b, 82c each time the worm gear is driven away from the second stop positions 82a, 82b, 82 c. For example, a given one of the second stop positions 82a, 82b, 82c for stopping the worm gear 48 may be changed each time the worm gear 48 is rotated past all of the second stop positions 82a, 82b, 82c (i.e., toward the first stop positions 80a, 80b, 80 c). Alternatively, a given one of the second stop positions 82a, 82b, 82c for stopping the worm wheel 48 may be changed each time the worm wheel 48 is rotated beyond some other predetermined position. In some embodiments, changing a given one of the second stop positions 82a, 82b, 82c for stopping the worm gear 48 to another one of the second stop positions 82a, 82b, 82c includes changing the given one of the second stop positions 82a, 82b, 82c in a predetermined pattern. For example, the stop position may be rotated in a repeating pattern (e.g., a, b, c …, or a, b, a, b …).

One of the first stop positions 80a, 80b, 80c and/or one of the second stop positions 82a, 82b, 82 for stopping the worm gear 48 may be changed using different methods, for example on a periodic time basis.

Table 1 shows the effect of a change in hand wheel position for a Single Pinion Electric Power Steering (SPEPS) having a plurality of stop positions spaced apart by two gear teeth 70 on the worm gear 48. Specifically, Table 1 shows the stop positions two gear teeth 70 apart, which corresponds to a handwheel variation of +/-10. Table 2 shows the effect of a change in hand wheel position for a Double Pinion Electric Power Steering (DPEPS) having a plurality of stop positions spaced apart by two gear teeth 70 on the worm gear 48. Specifically, Table 2 shows the stop positions spaced two gear teeth 70 apart, which corresponds to a handwheel variation of +/-8.54545.

TABLE 1

TABLE 2

DPEPS
			Number of skipped teeth		2
Tooth number (Gear)		72
			Auxiliary gear angle change	°	10
Auxiliary pinion C factor	mm/360°	47
			Rack stroke change (+/-)	mm	1.30556
Drive pinion C factor	mm/360°	55
			Hand wheel angle change (+/-)	°	8.54545

Table 3 shows the effect of a change in hand wheel position for a Single Pinion Electric Power Steering (SPEPS) having multiple stop positions spaced apart by 1.5 gear teeth 70 on the worm gear 48. Specifically, Table 3 shows the stop positions of the gear teeth 70 spaced 1.5 apart, which corresponds to a handwheel variation of +/-7.5. Table 4 shows the effect of a change in hand wheel position for a Double Pinion Electric Power Steering (DPEPS) having multiple stop positions separated by 1.5 gear teeth 70 on the worm gear 48. Specifically, Table 4 shows the stop positions of the gear teeth 70 spaced 1.5 apart, which corresponds to a handwheel variation of +/-6.40909.

TABLE 3

TABLE 4

DPEPS
			Number of skipped teeth		1.5
Tooth number (Gear)		72
			Auxiliary gear angle change	°	7.5
Auxiliary pinion C factor	mm/360°	47
			Rack stroke change (+/-)	mm	0.97917
Drive pinion C factor	mm/360°	55
			Hand wheel angle change (+/-)	°	6.40909

The number of stop positions and the spacing between the plurality of stop positions is selected as a trade-off between the change in hand wheel angle and the effect of reducing wear on the worm gear 48. Worm gear wear may be reduced by using more stop positions and/or more spaced stop positions. However, increasing the number and/or increasing the spacing between stop positions may result in an increase in the change in hand wheel angle, which may result in the EPS system 40 not reaching the full range of steering travel.

A method for controlling a machine is also provided. The method comprises the following steps: rotating the drive shaft 60 by the motor 19; the worm wheel 48 is driven by the worm 47 coupled with the driving shaft 60 such that the worm wheel 48 is rotated in a first direction; stopping the motor 19 from rotating the drive shaft 60 in response to the worm gear 48 rotating in the first direction to a given one of the plurality of first stop positions 80a, 80b, 80 c; and changing a given one of the first stop positions 80a, 80b, 80c to another one of the first stop positions 80a, 80b, 80 c.

In some embodiments, the machine is configured to perform at least one of: apply assist torque to the steering system 40 of the vehicle, and control the steering system 40. For example, the machine may be all or part of an Electric Power Steering (EPS) system 40 of a motor vehicle.

In some embodiments, the step of changing the given one of the first stop positions 80a, 80b, 80c to another one of the first stop positions 80a, 80b, 80c is performed each time the worm gear 48 is driven away from the given one of the first stop positions 80a, 80b, 80 c. In some embodiments, the step of changing a given one of the first stop positions 80a, 80b, 80c to another one of the first stop positions 80a, 80b, 80c includes changing the given one of the first stop positions 80a, 80b, 80c in a predetermined pattern.

In some embodiments, adjacent ones of the first stop positions 80a, 80b, 80c are spaced from one another by one gear tooth of the worm gear 48. In some embodiments, adjacent ones of the first stop positions 80a, 80b, 80c are spaced from each other by an amount between one of the worm gears 48 and two of the gear teeth 70. In some embodiments, adjacent ones of the first stop positions 80a, 80b, 80c are spaced from one another by two or more gear teeth 70 of the worm gear 48. In some embodiments, adjacent ones of the first plurality of stop positions 80a, 80b, 80c are spaced from each other by an amount between one of the worm gear 48 and two of the gear teeth 70.

In some embodiments, the method for controlling a machine further comprises the steps of: driving the worm gear 48 via the worm such that the worm gear 48 rotates in a second direction opposite the first direction; stopping the motor from rotating the drive shaft in response to the worm gear 48 rotating in the second direction to a given one of the plurality of second stop positions 82a, 82b, 82 c; and changing a given one of the second stop positions 82a, 82b, 82c to another one of the second stop positions 82a, 82b, 82 c.

In some embodiments, the step of changing the given one of the second stop positions 82a, 82b, 82c to another one of the second stop positions 82a, 82b, 82c is performed each time the worm gear 48 is driven away from the given one of the second stop positions 82a, 82b, 82 c. In some embodiments, the step of changing the given one of the second stop positions 82a, 82b, 82c to another one of the second stop positions 82a, 82b, 82c includes changing the given one of the second stop positions 82a, 82b, 82c in a predetermined pattern.

In some embodiments, adjacent ones of the second stop positions 82a, 82b, 82c are spaced from one another by one gear tooth of the worm gear 48. In some embodiments, adjacent ones of the second stop positions 82a, 82b, 82c are spaced from each other by an amount between one of the worm gears 48 and two of the gear teeth 70. In some embodiments, adjacent ones of the second stop positions 82a, 82b, 82c are spaced from one another by two or more gear teeth 70 of the worm gear 48. In some embodiments, adjacent ones of the plurality of second stop positions 82a, 82b, 82c are spaced from each other by an amount between one of the worm gears 48 and two of the gear teeth 70.

A method for controlling a power steering system 40 in a vehicle is also provided. The method comprises the following steps: rotating the drive shaft 60 by the motor 19; the worm wheel 48 is driven by the worm 47 coupled with the driving shaft 60 such that the worm wheel 48 is rotated in a first direction; stopping the motor 19 from rotating the drive shaft 60 in response to the worm gear 48 rotating in the first direction to a given one of the plurality of first stop positions 80a, 80b, 80 c; and changing a given one of the plurality of first stop positions 80a, 80b, 80c to another one of the plurality of first stop positions 80a, 80b, 80 c.

In some embodiments, the method for controlling the power steering system 40 further comprises the steps of: driving the worm wheel 48 by the worm 47 so that the worm wheel 48 rotates in a second direction opposite to the first direction; stopping the motor 19 from rotating the drive shaft 60 in response to the worm gear 48 rotating in the second direction to a given one of the plurality of second stop positions 82a, 82b, 82 c; and changing a given one of the plurality of second stop positions 82a, 82b, 82c to another one of the plurality of second stop positions 82a, 82b, 82 c.

The systems and methods of the present disclosure may have several advantages over conventional systems and methods for operating a machine including a turbine. The system and method of the present disclosure may extend the useful life of a worm gear by distributing wear over a larger area of the worm gear. Further, the systems and methods of the present disclosure may allow a gear set to apply a higher torque than a gear set using conventional end-of-travel limits. For example, a gear set rated at 100Nm using conventional end of travel limits may be rated at 106Nm using a plurality of software defined end of travel limits as provided by the systems and methods of the present disclosure.

While the disclosure has been described in detail in connection with only a limited number of embodiments, it should be understood that the disclosure is not limited to those disclosed embodiments, but, on the contrary, may be modified to incorporate any number of variations, alterations, substitutions or equivalents not heretofore described, but which are commensurate with the scope of the disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that aspects of the disclosure may include only some of the described embodiments or combinations of various embodiments. Accordingly, the disclosure should not be viewed as limited by the foregoing description.