CN102468802B - Feedback switching device and method driven by servo motor - Google Patents

Abstract

A feedback switching device and method for servo motor drive has a novel feedback switching design, which can make the servo motor drive control loop actively switch the feedback mode along with the servo motor running speed, when the servo motor runs at high speed, the sensorless position estimation feedback technique is used as the feedback mode, conversely, when the servo motor runs at low speed, the feedback mode is automatically switched to the position sensing feedback technique. The feedback switching device and the method can meet the development requirements of the related field of servo motor drive control on multifunction, high performance and low cost. The technical bottleneck that the position sensing feedback technology or the non-sensing position estimation feedback technology cannot completely meet the application in the wide speed range when the servo drive system is applied to the wide speed range can be further solved.

Description

Feedback switching device and method driven by servo motor

technical field

The present invention relates to servo motor drive, and more specifically, to a servo motor drive feedback switching device and method capable of actively switching feedback modes along with the running speed of the servo motor.

Background technique

Servo motor drive is an important technology widely used in modern industry. Its current development direction is mainly to improve performance and reduce cost. In response to cost considerations, the improvement of performance and the increase of functions are also produced. corresponding needs. In various applications, some servo motors must operate in a very wide range of operating speeds, and the key factor in how the servo motor driver can effectively improve performance and reduce costs lies in the construction of the so-called speed control architecture.

For example, if the designer uses position sensing components such as encoders or resolvers to build a speed control structure, that is, uses position sensing feedback technology to build a speed control structure, when the servo motor is running at a low speed, As long as the bandwidth of the position signal is lower than that of the position sensor, the servo motor driver can receive the position signal correctly. However, if the motor speed is too high, so that the frequency of the position signal is higher than the bandwidth of the position signal receiver, the position signal will be distorted. Therefore, under the high-speed operation of the servo motor, other technologies must be used for processing. In order to solve this problem, the industry has developed a method of applying sensorless position estimation feedback technology to a high-speed motor to estimate the angle of the motor and then build a speed control framework.

Although the development of these two feedback technologies has become more and more mature, the current setting method of the servo motor driver is that the user must first decide whether to use the position sensing element to build the speed control structure before the servo motor runs, or to decide first Use sensorless position estimation feedback technology to build a speed control structure, but during the operation of the servo motor, the speed control structure set by the user cannot make corresponding elastic changes with the motor speed. The drive still has the problem of not being able to precisely control the servo motor. Specifically, if the user sets the speed control structure with position sensing feedback technology at the beginning, when the speed of the servo motor increases beyond a certain standard, the position signal obtained by the position sensing feedback technology will be distorted. As a result, the servo motor driver cannot obtain correct position information. If the user sets the speed control structure with sensorless position estimation feedback technology at the beginning, when the speed of the servo motor decreases below a certain standard, the accuracy of the position signal obtained by the sensorless position estimation feedback technology will start to lose accuracy, so that the servo motor driver will not be able to obtain correct position information. It can be seen that if this problem can be solved, the speed control performance of the servo motor driver will be greatly improved.

Therefore, if there is a servo motor drive feedback switching device and method that can automatically set or switch the feedback mechanism according to the operating speed of the servo motor, it will be able to effectively provide the cost-effectiveness required by the manufacturer. Suggestions and teachings are provided to help improve this problem.

Therefore, how to propose a servo motor drive feedback switching device and method that can solve various deficiencies in the known technology is a technical problem that all circles are eager to solve.

Contents of the invention

In view of the shortcomings of the above-mentioned known technologies, the main purpose of the present invention is to provide a feedback switching device and method for enabling the servo motor drive control loop to actively switch the feedback mode according to the running speed of the servo motor.

To achieve the above and other objectives, the present invention provides a servo motor-driven feedback switching device, which is applied in a control loop with a servo motor. The servo motor-driven feedback switching device includes: a current sensor for sensing The current supplied to the servo motor, and output a corresponding current feedback signal according to the sensed current; the position sensor is used to sense the position of the servo motor, and output a corresponding position sensor according to the sensed position signal; a position estimator, used to receive the current feedback signal of the current sensor, and output a corresponding position estimation signal according to the current feedback signal; and a feedback switching comparator, with predetermined switching conditions, used to receive the position sensor The detection signal and the position estimation signal, and select one of the position detection signal and the position estimation signal as the position feedback signal based on the predetermined switching condition.

In addition, the present invention further provides a feedback switching method driven by a servo motor, which is applied in a control loop with a servo motor, and the initial operating speed of the servo motor is in a low speed state. The feedback switching method driven by a servo motor includes the following steps : (1) using a current sensor to sense the current supplied to the servo motor, so as to output a corresponding current feedback signal according to the sensed current, and make the position sensor sense the position of the servo motor, To output the corresponding position sensing signal, and make the position estimator receive the current feedback signal, so as to output the corresponding position estimation signal according to the current feedback signal; (2) make the speed calculation module receive the position sensor output by the position sensor The measured signal and the position estimation signal output by the position estimator to generate corresponding first speed signal and second speed signal respectively, and make the comparison module receive the first speed signal and the second speed signal; (3) make the The comparison module compares the first speed signal with a predetermined switching condition to determine whether the first speed signal is higher than the switching condition, if yes, then proceed to step (4), if not, then proceed to step (6 ); (4) make the switching module select the output of the position estimation signal as a position feedback signal; (5) make the comparison module compare the second speed signal with the predetermined switching condition to determine whether the second speed signal If it is lower than the predetermined switching condition, then go to step (6), if not, go back to step (4); and (6) let the switching module choose to output the position sensing signal as a position feedback signal.

Furthermore, the present invention further provides a feedback switching method driven by a servo motor, which is applied in a control loop with a servo motor, and the initial operating speed of the servo motor is in a high-speed state. The feedback switching method driven by the servo motor includes the following Steps: (1) Make the current sensor arranged on the power supply path of the servo motor sense the current supplied to the servo motor, so as to output a corresponding current feedback signal according to the sensed current, and make the position sensing The device senses the position of the servo motor to output a corresponding position sensing signal, and makes the position estimator receive the current feedback signal to output a corresponding position estimation signal according to the current feedback signal; (2) makes the speed calculation The module receives the position sensing signal output by the position sensor and the position estimation signal output by the position estimator to generate corresponding first speed signal and second speed signal respectively, and makes the comparison module receive the first speed signal and the second speed signal The second speed signal; (3) make the comparison module compare the second speed signal with a predetermined switching condition to judge whether the second speed signal is lower than the switching condition, if so, proceed to step (4 ), if not, proceed to step (6); (4) make the switching module select the output of the position sensing signal as the position feedback signal; (5) make the comparison module compare the first speed signal with the switching condition Compare to determine whether the first speed signal is higher than the predetermined switching condition, if yes, then proceed to step (6), if not, then return to step (4); and (6) make the switching module select the The position estimate signal is output as a position feedback signal.

Compared with the known technology, the present invention can not only effectively reduce the cost of the manufacturer, improve product functionality, but also effectively improve the flexibility of the servo motor driver applied to the servo drive system with a wide speed range, and improve the overall operating efficiency of the servo motor.

Description of drawings

FIG. 1 is a structural diagram depicting a feedback switching device driven by a servo motor according to an embodiment of the present invention;

Fig. 2 is a schematic circuit diagram of the feedback switching comparator in Fig. 1;

3 is a schematic diagram illustrating the operation of a feedback switching device driven by a servo motor according to an embodiment of the present invention;

FIG. 4 is a flow chart depicting the steps of a feedback switching method driven by a servo motor according to an embodiment of the present invention; and

FIG. 5 is a flowchart depicting the steps of another servo motor-driven feedback switching method according to an embodiment of the present invention.

[Description of main component symbols]

Feedback switching device driven by 100 servo motors

102 position command 103 PID controller

104 speed command 105 PID controller

106 current command 107 PID controller

108 Current feedback signal 109 Power module

110 position feedback signal 111 current sensor

112 Speed feedback signal 113 Servo motor

115 position sensor 115a position sensing signal

117 position estimator 117a position estimate signal

119 Feedback switching comparator 121 Speed feedback generator

201 speed calculation module 201a first speed signal

201b second speed signal 202 switching condition

203 comparison module 203a speed comparison result

205 switching module 302 hours

304 points

Feedback switching method for 400 servo motor drive

Steps S402-S412

Feedback switching method driven by 500 servo motor

Steps S502-S512

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific examples, and various modifications and changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

The feedback switching device and method for servo motor drive proposed by the present invention are applied in the control loop of servo motor drive, in order to overcome the problem that the position data will be distorted when the motor is running at high speed in the position sensing feedback technology. To overcome various problems such as the position data cannot meet the speed accuracy required by the user when the motor is running at low speed using sensorless position estimation feedback.

Please refer to FIG. 1 , which shows a schematic structural diagram of a feedback switching device 100 driven by a servo motor according to an embodiment of the present invention. In this embodiment, the servo motor-driven feedback switching device 100 is applied in a servo motor drive control loop with a servo motor 113, and at least includes a position sensor 115, a position estimator 117, and a feedback switching comparator 119, And optionally, a speed feedback generator 121 such as a differentiator is provided.

The servo motor drive control loop can also include proportional-integral-derivative (proportional-integral-derivative) controllers 103 , 105 , 107 , hereinafter referred to as PID controllers 103 , 105 , 107 , and a power module 109 . Wherein, the PID controller 103 can receive the position command 102 , the PID controller 105 can receive the speed command 104 , and the PID controller 107 can receive the current command 106 and is connected to the power module 109 .

The current sensors 111 are disposed on the power supply path of the servo motor 113 to sense the current supplied to the servo motor 113 and output a corresponding current feedback signal 108 according to the sensed current.

The position sensor 115 can be arranged on the servo motor 113 to sense the position of the servo motor 113, and output a corresponding position sensing signal 115a according to the sensed position. In this embodiment, the position sensing The device 115 can be an encoder or a resolver for encoding the position of the servo motor 113 .

The position estimator 117 is connected to the current sensors 111 for receiving the current feedback signal 108 output by the current sensor 111 and outputting a corresponding position estimation signal according to the current feedback signal 108 output by the current sensor 111 117a.

The feedback switching comparator 119 is used to receive the position sensing signal 115a, the position estimation signal 117a, and the switching condition (hereinafter referred to as switching condition) predefined by the user, and select the position sensing signal based on the switching condition. One of the measured signal 115 a and the position estimated signal 117 a is output as the position feedback signal 110 .

Therefore, when the servo motor drive control loop operates at a lower speed, the feedback switching comparator 119 can automatically select the position sensing signal 115 a to be output as the position feedback signal 110 , thereby satisfying the requirement of high efficiency. When the servo motor drive control loop operates at a higher speed, the feedback switching comparator 119 can automatically select the position estimation signal 117a to be output as the position feedback signal 110, thereby satisfying the wide speed operation requirement.

Further, the position feedback signal 110 output by the feedback switching comparator 119 can be combined with the position command 102 for the PID controller 103 to receive and generate the speed command 104. At the same time, the position feedback signal 110 output by the feedback switching comparator 119 It can also be transmitted to the speed feedback generator 121 for it to generate the speed feedback signal 112, and after the speed feedback signal 112 is combined with the speed command 104, it can be received by the PID controller 105 to generate the current command 106, and the current command 106 After being combined with the current feedback signal 108 , it can be provided to the PID controller 107 for reception, and the PID controller 107 can also be connected to the power module 109 so that the power module 109 can control the relative speed of the servo motor 113 .

In actual implementation, firstly, the current sensor 111 disposed on the power supply path of the servo motor 113 can sense the current of the servo motor 113 and generate a corresponding current feedback signal 108 according to the sensed current. The current feedback signal 108 is transmitted to the position estimator 117 and combined with the current command 106, and the position estimator 117 generates/outputs the corresponding position according to the current feedback signal 108 after receiving the current feedback signal 108 Signal 117a is estimated. At the same time, the position sensor 115 senses the position of the servo motor 113 and generates/outputs a corresponding position sensing signal 115a according to the position.

Next, the feedback switching comparator 119 receives the position sensing signal 115a and the position estimation signal 117a, and selects one of the position sensing signal 115a and the position estimation signal 117a based on the switching condition predefined by the user. One output is the position feedback signal 110 . The operation details of the feedback switching comparator 119 will be described in detail below.

Then, the speed feedback generator 121 generates a speed feedback signal 112 based on the position feedback signal 110 , and the speed feedback signal 112 is combined with the speed command 104 .

Please refer to FIG. 2 in conjunction with FIG. 1 , wherein FIG. 2 is a schematic circuit diagram showing the feedback switching comparator 119 in FIG. 1 . As shown in the figure, the feedback switching comparator 119 includes two speed calculation modules 201 , a comparison module 203 , and a switching module 205 .

The speed calculation modules 201 can be differentiators for respectively receiving the position sensing signal 115a output by the position sensor 115 and the position estimation signal 117a output by the position estimator 117 to generate corresponding first speed signals 201a respectively. with the second speed signal 201b. In actual implementation, the two speed calculation modules 201 shown in the figure can be integrated into a single one.

The comparison module 203 is used for receiving the switching condition 202 predefined by the user, the first speed signal 201a, and the second speed signal 201b, and comparing one of the first speed signal 201a and the second speed signal 201b with the The switching condition 202 is compared to output a speed comparison result 203a. It should be noted here that, in this embodiment, an additional controller or logic circuit or software (not shown) can be used to control the comparison module 203, and the comparison module 203 can also have a hysteresis characteristic, and set A specific hysteresis range is defined, and the hysteresis range and the switching condition 202 are used as comparison criteria to prevent the speed comparison result 203a output by the comparison module 203 from oscillating near a threshold value. The switching condition 202 can be set at any point on the characteristic curve of the servo motor 113 as long as the position feedback is correct.

The switching module 205 is used to receive the position sensing signal 115a output by the position sensor 115 and the position estimation signal 117a output by the position estimator 117, and select the position sensing signal to be received based on the speed comparison result 203a. One of the signal 115 a and the position estimation signal 117 a is output as the position feedback signal 110 .

In order to understand the feedback switching device driven by a servo motor of the present invention more clearly, please refer to FIG. 3 in conjunction with FIG. 2 , wherein FIG. 3 is a schematic diagram showing the operation of the feedback switching device 100 driven by a servo motor according to an embodiment of the present invention. As shown in the figure, the hysteresis range can be combined with the switching condition 202 to form a relatively flexible comparison standard, and the speed indicated by the vertical axis in FIG. 3 represents the running speed of the servo motor 113 .

Before the time point 302 , the user can set to use the position sensing signal 115 a as the position feedback signal 110 directly, and use the position sensing signal 115 a as the basis for controlling the speed of the servo motor 113 . However, at this time, the comparison module 203 can also compare the second speed signal 201b lower than the user-defined switching condition 202, that is, it can be judged that the speed of the servo motor 113 is in a low speed state, so the comparison module 203 will also output accordingly. The speed comparison result 203 a is sent to the switching module 205 , so that the switching module 205 selects to output the position sensing signal 115 a as the position feedback signal 110 , and then uses the position sensing signal 115 a as the basis for controlling the speed of the servo motor 113 .

When the time goes to the time point 302 (the high point of the hysteresis range), the comparison module 203 will compare that the first speed signal 201a is higher than the switching condition 202, that is, the speed of the servo motor 113 has been running to a high speed state. At this time, The comparison module 203 will output the speed comparison result 203a to the switching module 205 accordingly, so that the switching module 205 performs a switching action so as to select the output of the position estimation signal 117a as the position feedback signal 110, and then start to use the position estimation signal 117a as the position feedback signal 110. The basis for the speed control of the servo motor 113.

And when the time goes to the time point 304 (the low point of the hysteresis range), the comparison module 203 will compare that the second speed signal 201b is lower than the user-defined switching condition 202, that is, the speed of the servo motor 113 runs to a low speed state , at this time, the comparison module 203 will output the speed comparison result 203a to the switching module 205 accordingly, so that the switching module 205 can switch again, so as to select the output of the position sensing signal 115a as the position feedback signal 110, and then start again The position sensing signal 115a is used as the basis for controlling the speed of the servo motor 113 .

Please refer to FIG. 4 in conjunction with FIG. 1 and FIG. 2 to clearly understand a step-by-step process of a servo motor-driven feedback switching method 400 according to an embodiment of the present invention, and the servo motor-driven feedback switching method 400 is applied to a servo with a servo motor. In the motor drive control loop. What needs to be explained first is that the feedback switching method 400 driven by the servo motor is applied in a running state where the initial running speed of the servo motor is low.

First, in step S402, the current sensor provided on the power supply path of the servo motor is used to sense the current supplied to the servo motor, so as to output a corresponding current feedback signal according to the sensed current, and use The position sensor senses the position of the servo motor to output a corresponding position sensing signal, and the position estimator receives the current feedback signal to output a corresponding position estimation signal according to the current feedback signal, and simultaneously uses the position The sensing signal is used as a position feedback signal, and then proceed to step S404.

In step S404, the speed calculation module receives the position sensing signal output by the position sensor and the position estimation signal output by the position estimator, and generates a corresponding first speed signal and a second speed signal respectively. The comparison module receives a predetermined switching condition, the first speed signal, and the second speed signal, and then proceeds to step S406.

In step S406, use the comparison module to compare the first speed signal with the predetermined switching condition to determine whether the first speed signal is higher than the predetermined switching condition, if yes, go to step S408, if not, Then go to step S412.

In step S408, the switching module selects to output the position estimation signal as a position feedback signal, and then proceeds to step S410.

In step S410, use the comparison module to compare the second speed signal with the predetermined switching condition to determine whether the second speed signal is lower than the predetermined switching condition, if yes, go to step S412, if not , return to step S408.

In step S412, the switching module selects to output the position sensing signal as a position feedback signal, and then returns to step S406.

In the feedback switching method 400 driven by a servo motor, the position sensor is an encoder or a resolver for encoding the position of the servo motor. The comparison module may have hysteresis characteristics, and a specific hysteresis range is set. Therefore, in step S406, the comparison module uses the hysteresis range and the predetermined switching condition as whether the first speed signal is higher than The judgment standard of the switching condition, and in step S410, the comparison module can also use the hysteresis range and the predetermined switching condition as the judgment standard of whether the second speed signal is lower than the switching condition.

Please refer to FIG. 5 together with FIG. 1 and FIG. 2 to clearly understand the flow of steps of another feedback switching method 500 driven by a servo motor according to an embodiment of the present invention. Certainly, the feedback switching method 500 for servo motor driving is also applied in a servo motor driving control loop with a servo motor. What needs to be explained first is that the feedback switching method 500 driven by a servo motor is applied in a running state where the initial running speed of the servo motor is already a high speed.

First, in step S502, the current supplied to the servo motor is sensed by a current sensor provided on the power supply path of the servo motor, so as to output a corresponding current feedback signal according to the sensed current, and use The position sensor senses the position of the servo motor to output a corresponding position sensing signal, and the position estimator receives the current feedback signal to output a corresponding position estimation signal according to the current feedback signal, and simultaneously sets Using the position estimation signal as the position feedback signal, then proceed to step S504.

In step S504, the speed calculation module receives the position sensing signal output by the position sensor and the position estimation signal output by the position estimator to generate corresponding first speed signals and second speed signals respectively, and compare the The module receives a predetermined switching condition, the first speed signal, and the second speed signal, and then proceeds to step S506.

In step S506, use the comparison module to compare the second speed signal with the predetermined switching condition to determine whether the second speed signal is lower than the switching condition set by the user, if yes, go to step S508 , if not, go to step S512.

In step S508, the switching module selects to output the position sensing signal as a position feedback signal, and then proceeds to step S510.

In step S510, use the comparison module to compare the first speed signal with the switching condition to determine whether the first speed signal is higher than the predetermined switching condition, if yes, go to step S512, if not, then Go back to step S508.

In step S512, the switching module selects to output the position estimation signal as a position feedback signal, and then returns to step S506.

In the feedback switching method 500 driven by a servo motor, the position sensor is an encoder or a resolver for encoding the position of the servo motor. The comparison module may have a hysteresis characteristic, and a specific hysteresis range is set. Therefore, in step S506, the comparison module uses the hysteresis range and the predetermined switching condition as whether the second speed signal is low or not. In step S510 , the comparing module uses the hysteresis range and the predetermined switching condition as the judging criterion of whether the first speed signal is higher than the switching condition.

In summary, the feedback switching device and method for servo motor drive of the present invention, in addition to providing an automated feedback switching mechanism, can further improve the functionality of the servo motor drive control loop. For servo motors with wide speed range applications The driving control can actually avoid the problem of insufficient operational flexibility in the known technology, thereby improving the overall operating efficiency of the servo motor.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Those skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be listed in the protection scope of the claims.

Claims (13)

1. a feedback switching device for servo motor driven, it is applied in the control loop with servo motor, it is characterized in that, and the feedback switching device of this servo motor driven comprises:

Current sensor, is supplied to the electric current of this servo motor, and exports corresponding current feedback signal according to the electric current of institute's sensing in order to sensing;

Position sensor, in order to the position of this servo motor of sensing, and exports corresponding location sensing signal according to the position of this servo motor of institute's sensing;

Position estimator, in order to receive this current feedback signal, and exports corresponding location estimation signal according to this current feedback signal;

Feedback is switched comparator, there is predetermined switching condition, in order to receive this location sensing signal and this location estimation signal, and one of them using this location sensing signal and this location estimation signal exported as position feed back signal according to this predetermined switching condition selection; And

Speed feedback generation device, in order to receive this position feed back signal, and produce and export corresponding feedback speed signal according to this position feed back signal, and this control loop receiving position order, speed command and current order, to control the running speed of this servo motor.

2. the feedback switching device of servo motor driven as claimed in claim 1, is characterized in that, this position sensor is the encoder in order to being encoded in the position of this servo motor or separates hornwork.

3. the feedback switching device of servo motor driven as claimed in claim 1, is characterized in that, this feedback is switched comparator and comprised:

Speed calculation module, in order to receive the location sensing signal of being exported by this position sensor and the location estimation signal of being exported by this position estimator, to produce respectively corresponding First Speed signal and second speed signal;

Comparison module, in order to receive this First Speed signal and this second speed signal, and compares one of them and this switching condition of this First Speed signal and this second speed signal, with output speed comparative result; And

Handover module, in order to receive the location sensing signal of this position sensor output and the location estimation signal of this position estimator output, and one of them using this location sensing signal receiving and this location estimation signal exported as this position feed back signal based on this speed comparative result selection.

4. the feedback switching device of servo motor driven as claimed in claim 3, is characterized in that, this comparison module has hysteresis characteristic, and is set with specific magnetic hysteresis scope, and this comparison module is with this magnetic hysteresis scope and this switching condition standard as a comparison.

5. the feedback switching device of servo motor driven as claimed in claim 1, is characterized in that, this position command combines with this position feed back signal that this feedback switching comparator is exported.

6. the feedback switching device of servo motor driven as claimed in claim 1, is characterized in that, this speed command combines with this feedback speed signal that this speed feedback generation device produces.

7. the feedback switching device of servo motor driven as claimed in claim 1, is characterized in that, this current feedback signal that this current order is exported with this current sensor combines.

8. a feedback changing method for servo motor driven, it is applied in the control loop with servo motor, and the initial running speed of this servo motor is in lower-speed state, it is characterized in that, and the feedback changing method of this servo motor driven comprises the following steps:

(1) with current sensor, the electric current that is supplied to this servo motor is carried out to sensing, to export corresponding current feedback signal according to the electric current of institute's sensing, and make position sensor carry out sensing to the position of this servo motor, to export corresponding location sensing signal, and with position estimator, receive this current feedback signal, to export corresponding location estimation signal according to this current feedback signal;

(2) make speed calculation module receive the location sensing signal of this position sensor output and the location estimation signal of this position estimator output, to produce respectively corresponding First Speed signal and second speed signal, and receive this First Speed signal and this second speed signal with comparison module;

(3) make this comparison module that this First Speed signal and predetermined switching condition are compared, to judge that whether this First Speed signal is higher than this switching condition, if so, proceed to step (4), if not, proceed to step (6);

(4) using handover module, select this location estimation signal to export as position feed back signal;

(5) with this comparison module, this second speed signal and this predetermined switching condition are compared, to judge that this second speed signal, whether lower than this predetermined switching condition, if so, proceeds to step (6), if not, get back to step (4); And

(6) using handover module, select this location sensing signal to export as position feed back signal.

9. the feedback changing method of servo motor driven as claimed in claim 8, is characterized in that, this position sensor is the encoder in order to being encoded in the position of servo motor or separates hornwork.

10. the feedback changing method of servo motor driven as claimed in claim 8, it is characterized in that, this comparison module has hysteresis characteristic, and be set with specific magnetic hysteresis scope, and in step (3), this comparison module is the criterion higher than this switching condition whether using this magnetic hysteresis scope and this predetermined switching condition as this First Speed signal, and in step (5), this comparison module is the criterion lower than this switching condition whether using this magnetic hysteresis scope and this predetermined switching condition as this second speed signal.

The feedback changing method of 11. 1 kinds of servo motor driven, it is applied in the control loop with servo motor, and the initial running speed of this servo motor is in fast state, it is characterized in that, and the feedback changing method of this servo motor driven comprises the following steps:

(1) with current sensor, the electric current that is supplied to this servo motor is carried out to sensing, to export corresponding current feedback signal according to the electric current sensing, and with position sensor, sensing is carried out in the position of this servo motor, to export corresponding location sensing signal, and with position estimator, receive this current feedback signal, to export corresponding location estimation signal according to this current feedback signal;

(2) with speed calculation module, receive the location sensing signal of this position sensor output and the location estimation signal of this position estimator output, to produce respectively corresponding First Speed signal and second speed signal, and receive this First Speed signal and this second speed signal with comparison module;

(3) with this comparison module, this second speed signal and predetermined switching condition are compared, to judge that whether this second speed signal is lower than this switching condition, if so, proceed to step (4), if not, proceed to step (6);

(4) using handover module, select this location sensing signal to export as position feed back signal;

(5) with this comparison module, this First Speed signal and this switching condition are compared, to judge that this First Speed signal, whether higher than this predetermined switching condition, if so, proceeds to step (6), if not, get back to step (4); And

(6) using handover module, select this location estimation signal to export as position feed back signal.

The feedback changing method of 12. servo motor driven as claimed in claim 11, is characterized in that, this position sensor is the encoder in order to being encoded in the position of servo motor or separates hornwork.

The feedback changing method of 13. servo motor driven as claimed in claim 11, it is characterized in that, this comparison module has hysteresis characteristic, and be set with specific magnetic hysteresis scope, and in step (3), this comparison module is the criterion lower than this switching condition whether using this magnetic hysteresis scope and this predetermined switching condition as this second speed signal, and in step (5), this comparison module is the criterion higher than this switching condition whether using this magnetic hysteresis scope and this predetermined switching condition as this First Speed signal.

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