阅读说明：本技术 光栅尺动态误差的检测系统及检测方法 (System and method for detecting dynamic error of grating ruler ) 是由 徐全坤 黄振宇 阚侃 张向 谭翠媚 罗旭东 于 2020-07-09 设计创作，主要内容包括：本发明公开了光栅尺动态误差检测系统,包括第一装置,用于获取待测光栅尺的实时位置；第二装置,用于确定待测光栅尺的基准位置；信号采集控制器,将第一装置及第二装置获取的位置信号发送至计算机；计算机对接收到的位置信号进行比较,确定光栅尺的动态误差。该检测系统采用激光干涉作为长度基准,通过伺服直线电机实现光栅尺不同运行工况的模拟,设计了基于FPGA的双路信号采集处理系统,实现基准信号和实时信号的同步采集,通过数据存储和后续传输处理,对测量结果进行分析显示。(The invention discloses a grating ruler dynamic error detection system, which comprises a first device, a second device and a third device, wherein the first device is used for acquiring the real-time position of a grating ruler to be detected; the second device is used for determining the reference position of the grating ruler to be measured; the signal acquisition controller is used for sending the position signals acquired by the first device and the second device to the computer; and the computer compares the received position signals to determine the dynamic error of the grating ruler. The detection system adopts laser interference as a length reference, realizes the simulation of different operation working conditions of the grating ruler through a servo linear motor, designs a double-path signal acquisition and processing system based on the FPGA, realizes the synchronous acquisition of reference signals and real-time signals, and analyzes and displays the measurement result through data storage and subsequent transmission processing.)

1. Detection system of grating chi dynamic error, its characterized in that includes:

the first device is used for acquiring the real-time position of the grating ruler to be measured;

the second device is used for determining the reference position of the grating ruler to be measured;

the signal acquisition controller is used for sending the position signals acquired by the first device and the second device to the computer;

and the computer compares the received position signals to determine the dynamic error of the grating ruler.

2. The system for detecting the dynamic error of the grating ruler as claimed in claim 1, further comprising a guide rail and a movable slider capable of sliding along the direction of the guide rail; the second device comprises a laser interference system, and the laser interference system comprises a laser, an interference mirror and a reflecting mirror; the laser and the interference mirror are sequentially arranged on the guide rail; the reflecting mirror is positioned on the movable sliding block.

3. The system for detecting the dynamic error of the grating ruler as claimed in claim 1, wherein the first device comprises a grating ruler reading head, and the grating ruler reading head is fixed on a movable sliding block or a guide rail.

4. The system for detecting the dynamic error of the grating ruler according to any one of claims 1 to 3, wherein the information acquisition controller comprises a first data acquisition module, a second data acquisition module, a first attenuation circuit, a second attenuation circuit, an FPGA control module, and a data cache module;

the laser of the laser interference system is connected with the first attenuation circuit through the first data acquisition module; the grating ruler reading head is connected with the second attenuation circuit through the second data acquisition module; the first attenuation circuit and the second attenuation circuit are both connected with the FPGA control module, and the FPGA control module is connected with the computer through the data cache module.

5. The system for detecting the dynamic error of the grating ruler as claimed in claim 3, wherein the grating ruler reading head is driven by a grating ruler reading head driving system, the grating ruler reading head driving system comprises a servo linear motor, and the computer controls the servo linear motor through a servo linear motor controller;

the stator of the servo linear motor is fixed with the guide rail, the movable sliding block is fixed with the rotor of the servo linear motor, and the rotor of the servo linear motor can drive the movable sliding block to move together.

6. The system for detecting the dynamic error of the grating ruler as claimed in any one of claims 2 to 3 or 5, wherein a temperature sensor and a vibration sensor are further disposed on the guide rail.

7. The system for detecting dynamic error of a grating ruler as claimed in claim 2, wherein the guide rail is an air-float guide rail.

8. The detection method using the system for detecting the dynamic error of the grating ruler according to any one of claims 1 to 7, wherein the dynamic error of the grating ruler is obtained by comparing a real-time position of the dynamic state of the grating ruler to be detected with a reference position;

the real-time position of the grating ruler is a position curve of the movable sliding block measured under different speed and acceleration working conditions, and the reference position is a position curve of the movable sliding block measured by the grating ruler reference position determining device under the same working condition.

9. The method for detecting the dynamic error of the grating ruler according to claim 8, comprising the steps of:

(1) the computer sends speed and acceleration instructions to the servo linear motor servo controller, so that a rotor of the servo linear motor drives the movable sliding block and the grating ruler reading head to move together, and a signal acquired by the first device is processed by the signal processing system to obtain a dynamic real-time position curve P (T, v, a, T) of the grating ruler;

(2) in the movement process, the position curve L (T, v, a, T) obtained by processing the position signal of the movable slide block by the signal processing system is used as the reference position curve of the grating ruler;

(3) comparing the real-time position curve P (T, v, a, T) of the same set of grating ruler with the reference position curve L (T, v, a, T) to obtain the dynamic measurement error E (T, v, a, T) of the grating ruler, namely the formula (1)

E(t,v,a,T)＝P(t,v,a,T)-L(t,v,a,T) (1)

Wherein T is the measuring time, v is the moving speed of the moving slide block, a is the moving acceleration of the moving slide block, and T is the real-time environment temperature.

10. The method for detecting the dynamic error of the grating ruler according to claim 9, wherein the dynamic error of the grating ruler further comprises a dynamic backhaul error; the dynamic return error is the difference value of the dynamic measurement errors measured in two opposite movement directions, namely the equation (2)

ΔE(x,v,a,T)＝E_f(x,v,a,T)-E_b(x,v,a,T) (2)

Where x is the return error measurement position, E_f(x, v, a, T) is a dynamic measurement error in the first moving direction of the grating scale measured by the formula (1), E_b(x, v, a, T) is a dynamic measurement error of the grating scale in a direction opposite to the first moving direction measured by the equation (1).

Technical Field

The invention relates to the technical field of performance detection of a grating ruler, in particular to a system and a method for detecting dynamic errors of the grating ruler.

Background

The grating ruler is an important position feedback component and is widely applied to modern machining industries such as a numerical control machine tool and the like. High-performance grating scales, especially large-stroke high-precision absolute grating scales, are one of the technical bottlenecks of high-end full-closed-loop numerical control machines in China, and almost all rely on imports at present.

At present, some researches are carried out in the aspects of static and dynamic characteristics research and dynamic detection of the grating ruler at home. The Zhengdawn of Changchun bare engine researches static precision detection and correction method, the scheme mainly considers the influence of static geometric error on precision, and does not carry out dynamic error analysis. The influence of factors such as deformation of a workbench and a guide rail on the precision of the grating ruler is analyzed by the university of the fertilizer industry, but the measurement error analysis is static analysis, and the influence of factors such as the running speed change and the vibration of the grating ruler on the dynamic precision is not considered. The grating ruler dynamic detection system built by Wuyubin and the like of Shenzhen university can realize the functions of automatic control, data acquisition and the like of grating ruler detection through a computer, the detection process is carried out under the condition of low speed and uniform speed, dynamic factors such as different running speeds, acceleration and vibration of the grating ruler in the test process and static factors such as temperature and the like are not considered, and the system realizes the automation of the static detection process rather than the dynamic performance detection.

The method is characterized in that the method comprises the steps of measuring the dynamic error of a grating ruler, and measuring the dynamic error of the grating ruler under a specific working condition.

The static error of the grating ruler is the error between the stable reading and the reference position after the reading head of the grating ruler stops at a certain position; the dynamic error of the grating ruler refers to the error between the real-time dynamic reading of the grating ruler and the real-time reference position when the reading head moves in the working state of the grating ruler.

Disclosure of Invention

In order to solve the above problems, the present invention provides a system for detecting a dynamic error of a grating scale, which obtains a dynamic error of the grating scale by comparing a dynamic real-time position of the grating scale with a reference position, and can improve the measurement accuracy of the dynamic error of the grating scale. The method specifically comprises the following steps:

the first device is used for acquiring the real-time position of the grating ruler to be measured;

the second device is used for determining the reference position of the grating ruler to be measured;

the signal acquisition controller is used for sending the position signals acquired by the first device and the second device to the computer;

and the computer compares the received position signals to determine the dynamic error of the grating ruler.

In some embodiments, the grating scale head is coupled to a moving slide. The real-time position of the grating ruler is a curve formed by a series of positions of the movable sliding block measured under working conditions of different speeds, accelerations and the like, and the reference position is a position curve of the movable sliding block measured by the grating ruler reference position determining device under the same working condition.

In some embodiments, the grating ruler is calibrated by using a high-precision position testing system. The second device comprises a laser interference system, wherein the laser interference system comprises a laser, an interference mirror and a reflecting mirror; laser after laser interference system's laser instrument jets out is divided into two bundles with certain small angle by the interference mirror, and in inciding to the speculum, in the speculum reflects, returns to the interference mirror along new light path, returns the light inlet of laser after the interference mirror closes to accomplish the linear measurement, thereby confirm the reference position who obtains grating chi.

In some specific embodiments, the system for detecting the error of the grating ruler further comprises a guide rail and a movable sliding block which can slide along the direction of the guide rail; wherein the laser and the interference mirror are arranged on the guide rail in sequence; the reflecting mirror is positioned on the movable sliding block.

In some specific embodiments, the first device includes a grating ruler reading head, and the grating ruler reading head is used for acquiring a real-time position signal of the grating ruler, where the installation positions of the grating ruler and the grating ruler reading head are two cases:

(1) the grating ruler reading head is located on the movable sliding block, and the grating ruler is fixed on the guide rail, so that after the movable sliding block is displaced, the grating ruler reading head is also displaced, the relative distance between the grating ruler reading head and the grating ruler is changed, and the real-time position of the grating ruler is obtained.

(2) The grating ruler is located on the movable sliding block, and the grating ruler reading head is fixed on the guide rail, so that after the movable sliding block is displaced, the grating ruler is also displaced, and therefore the relative distance between the grating ruler reading head and the grating ruler is changed, and the real-time position of the grating ruler is obtained.

One of the difficulties in dynamic precision detection of a grating scale is high-speed synchronous acquisition of a real-time position signal of the grating scale to be detected and a reference position signal of the grating scale, and particularly, under the condition of high-speed operation, an error caused by a signal synchronous error is larger. The traditional data acquisition card based on a single chip microcomputer has the data reading speed of micro-second level, two paths of signals need to be read in turn in an alternate mode, the two-path signal acquisition needs several microseconds every time, the caused measurement error reaches several micrometers, and the detection requirement cannot be met for a high-precision grating ruler.

In order to avoid synchronization errors caused by signal acquisition, the invention designs a high-speed dual-channel synchronous data acquisition system, and in some specific embodiments, the information acquisition controller comprises a first data acquisition module, a second data acquisition module, a first attenuation circuit, a second attenuation circuit, an FPGA control module and a data cache module; the laser of the laser interference system is connected with the first attenuation circuit through the first data acquisition module; the grating ruler reading head is connected with the second attenuation circuit through the second data acquisition module; the first attenuation circuit and the second attenuation circuit are both connected with the FPGA control module, and the FPGA control module is connected with the computer through the data cache module.

In order to simulate the working condition of the grating ruler in actual use more accurately, in some specific embodiments, the grating ruler reading head movement driving system comprises a servo linear motor, the servo linear motor is controlled by a servo linear motor controller, and the servo linear motor controller is connected with a computer.

In some more specific embodiments, the servo linear motor comprises a rotor part and a stator part, wherein the rotor part is fixed with the movable sliding block, the stator part is fixed with the guide rail, when at least one set of detection data is generated through the computer, the computer sends a control signal to the servo linear motor controller so as to control and drive the servo linear motor to work, and the stator part moves to drive the movable sliding block to move together.

The laser, the interference mirror, the guide rail and the servo linear motor are arranged on the same working stand (shockproof stand).

In some specific embodiments, a temperature sensor and a vibration sensor are further arranged on the guide rail, and the temperature sensor and the vibration sensor are respectively used for monitoring the working temperature and the vibration condition of the guide rail.

In order to ensure the linearity and dynamic characteristics of the rail system, in some embodiments, the rail is an air bearing rail.

The grating ruler dynamic error detection system provided by the invention adopts the laser interference system as the length reference, realizes the simulation of different operation conditions of the grating ruler through the servo linear motor, designs the FPGA-based dual-path signal acquisition and processing system, realizes the synchronous acquisition of reference signals and real-time signals, and analyzes and displays the measurement result through data storage and subsequent transmission processing.

In a second aspect, the present invention further provides a method for performing grating scale dynamic error detection by using a grating scale dynamic error detection system, including the following steps:

(1) sending speed and acceleration instructions to a linear motor servo control system through a computer, enabling a rotor of a linear motor to drive a movable sliding block and a grating ruler reading head to move together, and processing signals acquired by the grating reading head through a signal processing system to obtain a dynamic real-time position curve P (T, v, a, T) of a grating ruler;

(2) in the movement process, a position curve L (T, v, a, T) obtained by processing a position signal of the moving slide block acquired by a reference position determining device (namely a laser, an interference mirror and a reflecting mirror) by a signal processing system is used as a reference position curve of the grating ruler;

(3) comparing the real-time position curve P (T, v, a, T) of the same set of grating ruler with the reference position curve L (T, v, a, T) to obtain the dynamic measurement error E (T, v, a, T) of the grating ruler, namely the formula (1)

E(t,v,a,T)＝P(t,v,a,T)-L(t,v,a,T) (1)

Wherein T is the measuring time, v is the moving speed of the moving slide block, a is the moving acceleration of the moving slide block, and T is the real-time environment temperature.

In some embodiments, the test data further includes a moving direction, and therefore it is further required to detect a return error, which is a difference between dynamic measurement errors measured in two opposite moving directions, that is, equation (2)

ΔE(x,v,a,T)＝E_f(x,v,a,T)-E_b(x,v,a,T) (2)

Where x is the return error measurement position, E_f(x, v, a, T) is a dynamic measurement error in the first moving direction of the grating scale measured by the formula (1), E_b(x, v, a, T) is a dynamic measurement error of the grating scale in a direction opposite to the first moving direction measured by the equation (1).

Drawings

FIG. 1 is a perspective view of a system for detecting dynamic errors of a grating ruler according to the present invention;

fig. 2 is a schematic diagram of a signal acquisition controller according to the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

As shown in fig. 1, an embodiment of the present invention provides a system for detecting a dynamic error of a grating scale, including: the grating scale reading head 4 is fixed on the moving slide block 3, the moving slide block 3 can slide on the guide rail 2, and the guide rail can be an air-float guide rail.

The device for determining the reference position signal of the grating ruler for acquiring the reference position signal can be a laser interference system, the system comprises a laser 5 and an interference mirror 6 which are fixedly arranged on the guide rail 2, a reflecting mirror 7 which is fixedly arranged on the movable sliding block 3, and the laser 5, the interference mirror 6 and the reflecting mirror 7 are aligned with each other in a light path in the direction of the guide rail 2. Therefore, the grating ruler dynamic error detection system can acquire the reference signal as the reference position signal through the laser interference system, and can realize higher-precision position reference.

The movable slide block 3 is driven by a grating scale reading head 4 moving and driving system to slide on the guide rail. The grating ruler reading head moving driving system comprises a servo linear motor 8, the servo linear motor 8 is controlled by a servo linear motor controller 9, and the servo linear motor controller 9 is connected with a computer 10.

The signal acquisition controller 11 is configured to collect the real-time position signal of the grating scale and the reference position signal of the grating scale and transmit the signals to the computer for processing. The signal acquisition controller 11 is provided with a first connecting terminal, a second connecting terminal and a third connecting terminal; the first connecting terminal is connected with the laser 5, the second connecting terminal is connected with the grating ruler reading head 4, and the third connecting terminal is connected with the computer 10.

The grating ruler dynamic error detection system of the embodiment adopts the laser interference system as the length reference, and corresponding instructions are input into the computer, so that the grating ruler reading head is driven to move, and different operation conditions of the grating ruler to be detected can be realized (for example, different speeds, acceleration and other conditions of the grating ruler can be realized). Easy to operate and control.

In this embodiment, the linear motor 8 is connected to the computer 10 through the linear motor servo controller 9, wherein: the linear motor 8 comprises a rotor part and a stator part, the rotor part is connected with the movable sliding block 3, and the stator part is fixed with the guide rail 2. The computer 10 controls the linear motor 8 through the linear motor servo controller 9, then controls the brake part to drive the movable slide block 3, and then the movable slide block 3 drives the grating ruler reading head 4 to move, thereby realizing the working conditions of different speeds and accelerations of the grating ruler 15. And then can detect and feed back each item parameter of grating chi motion state.

In this embodiment, in the detection system, the data transmission line of the grating scale reading head 4, the air inlet pipe of the air-floating guide rail, and the like can move together with the movable slider 3.

In this embodiment, the system for detecting dynamic error of the grating ruler further includes a temperature sensor 12 and a vibration sensor 13 that can be installed on the air-floating guide rail 2. The temperature sensor and the vibration sensor respectively monitor the temperature and the vibration condition of the test system, and provide temperature compensation and vibration compensation for reducing errors.

In this embodiment, the grating ruler 15 to be measured is fixed on the guide rail 2, and an air film is arranged between the movable slider 3 and the guide rail 2. Thus, the real-time position signal of the grating ruler is obtained by moving the grating ruler reading head 4 on the slide block 3.

In this embodiment, the system for detecting dynamic error of a grating scale further includes a stage 1 for fixing the air-floating guide rail 2 and the linear electronic stator, and the stage 1 may be, for example, a vibration-isolated marble stage. Other parts in the grating ruler dynamic error detection system are fixed on the shock insulation marble rack, so that the error in the measurement process can be further reduced.

Fig. 2 is a block diagram showing an embodiment of the signal acquisition controller 11.

As shown in fig. 2, the information acquisition controller 11 includes a first data acquisition module (i.e., a high-speed AD chip 1), a second data acquisition module (i.e., a high-speed AD chip 2), a first attenuation circuit, a second attenuation circuit, an FPGA control module, and a data cache module; the first data acquisition module is respectively connected with a laser of the laser interference system and the first attenuation circuit, and the second data acquisition module is respectively connected with the grating ruler reading head and the second attenuation circuit; the first attenuation circuit and the second attenuation circuit are both connected with the FPGA control module, the FPGA control module is connected with the data cache module, and the FPGA control module is connected with the computer through the data cache module. By parallel high-speed double-channel synchronous acquisition, delay errors caused by transmission of data to a computer in a high-speed acquisition process are avoided.

The high-speed AD chip 1 and the high-speed AD chip 2 simultaneously carry out two-way data acquisition, respectively acquire real-time position signals of the laser interference system and the grating ruler, and carry out signal conversion and post-processing by the FPGA after the signal attenuation processing of the attenuation circuit. The arrangement of the attenuation circuit avoids delay errors caused by transmission to a computer in the high-speed data acquisition process, and the computer reads the cached measurement data and performs post-processing and display.

An embodiment of the present invention provides a method for detecting a dynamic error of a grating scale, including the following steps:

(1) sending speed and acceleration instructions to a linear motor servo control system through a computer, enabling a rotor of a linear motor to drive a movable sliding block and a grating ruler reading head to move together, and processing signals acquired by the grating reading head through a signal processing system to obtain a dynamic real-time position curve P (T, v, a, T) of a grating ruler;

(2) in the movement process, a position curve L (T, v, a, T) obtained by processing a position signal of the moving slide block acquired by a reference position determining device (namely a laser, an interference mirror and a reflecting mirror) by a signal processing system is used as a reference position curve of the grating ruler;

(3) comparing the real-time position curve P (T, v, a, T) of the same set of grating ruler with the reference position curve L (T, v, a, T) to obtain the dynamic measurement error E (T, v, a, T) of the grating ruler, namely the formula (1)

E(t,v,a,T)＝P(t,v,a,T)-L(t,v,a,T) (1)

Wherein T is the measuring time, v is the moving speed of the moving slide block, a is the moving acceleration of the moving slide block, and T is the real-time environment temperature.

For step (1), the grating ruler dynamic error detection system generates at least one set of test data within the specification parameter range according to the specification parameters of the grating ruler to be detected, for example, the specification parameters generally include a speed range, an acceleration range, and the like (the general maximum working speed can reach 2m/s, and the maximum working acceleration is 100 m/s)²) The generated test data should be within the specification parameters of the grating ruler.

In the embodiment, the synchronous acquisition of the real-time position and the reference position is carried out through the test data, and the dynamic error continuous output of the grating ruler under different motion working conditions is obtained. And determining the dynamic error of the grating ruler, and establishing a relation model of the dynamic error and factors such as speed, acceleration, temperature, vibration and the like, so that the dynamic precision of the grating ruler in actual use is predicted, and the dynamic precision of the grating ruler is improved.

When the test data also includes the moving direction, it is also necessary to detect the dynamic return error, which is the difference between the dynamic measurement errors measured in the two opposite moving directions, that is, equation (2)

ΔE(x,v,a,T)＝E_f(x,v,a,T)-E_b(x,v,a,T) (2)

Where x is the return error measurement position, E_f(x, v, a, T) is a dynamic measurement error in the first moving direction of the grating scale measured by the formula (1), E_b(x, v, a, T) is a dynamic measurement error of the grating scale in a direction opposite to the first moving direction measured by the equation (1).

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.