Multi-motor synchronous force control method and system

Abstract

The application provides a multi-motor synchronous force control method and system, and the method comprises the following steps: obtaining total expected force of the multi-motor; calculating sub-expected force of each motor in the multi-motor according to the characteristics of each motor; setting an outer feedback loop for controlling each motor to operate according to the corresponding sub-expected force, and taking the synchronization error of each motor as a feedback item of the outer feedback loop; and setting an inner feedback loop for controlling each motor to operate according to the corresponding sub-expected force, and taking the output force error of each motor as a feedback item of the inner feedback loop. The scheme can ensure the synchronization of the multi-motor movement under the premise of realizing accurate force control, realize accurate force control output of high power, and meet the actual industrial demand.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and more particularly to a method and system for synchronous force control of multiple motors. Background Technology

[0002] In many industrial scenarios, there is a need for multiple motors to operate synchronously. For example, in a height-restricted structure, a large torque needs to be output. If a single high-power motor cannot meet the installation requirements, multiple motors can be connected in parallel and operated synchronously to meet the requirements.

[0003] Synchronous operation of motors places high demands on their synchronization. Currently, most solutions only consider position control modes for multi-motor synchronization, where each motor is driven to output the same desired motion trajectory. Depending on the control strategy, these can be categorized as equal control, master-slave control, adjacent coupling control, cross-coupling control, virtual spindle control, and deviation coupling control. However, multi-motor synchronous force control requires both precise force control and synchronization of displacement and velocity among the motors, essentially constituting a hybrid force / position control system, which is significantly more challenging. Furthermore, traditional methods that measure motor output torque using current or force sensors have limited application due to their high cost. Therefore, a method is needed that can ensure the synchronization of multi-motor motion while maintaining precise force control. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-motor synchronous force control method and system, which solves the problems of high difficulty and high cost in the existing technology of force / position hybrid control of multiple motors.

[0005] The technical solution provided by this invention is as follows:

[0006] This invention provides a multi-motor synchronous force control method, comprising the following steps:

[0007] Obtain the total expected force of multiple motors;

[0008] Based on the characteristics of each motor in a multi-motor system, calculate the expected sub-force of each motor.

[0009] An external feedback loop is set up to control each motor to operate according to the corresponding desired force, and the synchronization error of each motor is used as the feedback item of the external feedback loop.

[0010] An internal feedback loop is set up to control each motor to operate according to the corresponding desired sub-force, and the output force error of each motor is used as the feedback item of the internal feedback loop.

[0011] When performing high-power force control output, by acquiring the total desired force of multiple motors and the characteristics of each motor, the sub-desired force of each motor can be calculated. At the same time, when controlling each motor to run according to its corresponding sub-desired force, by setting up external and internal feedback loops, and using the synchronization error of each motor as the feedback term of the external feedback loop and the output force error of each motor as the feedback term of the internal feedback loop, precise force control can be achieved in a limited space, while ensuring the synchronization of the movement of multiple motors, thus meeting more industrial needs.

[0012] Specifically, by distributing the expected force curve of each motor according to the total expected force and making each motor execute according to the expected force, precise control can be achieved, and the displacement and speed of each motor can be kept highly synchronized.

[0013] In addition, control is achieved through two loops. The inner loop is a high-speed force feedback loop, which designs the control rate based on the motor output force error to make the motor output the corresponding desired force. The outer loop is a low-speed motion synchronization error loop, which designs the control rate based on the differences in displacement and speed of each motor to further ensure that each motor keeps running synchronously.

[0014] In some implementations, using the synchronization error of each motor as the feedback term of the external feedback loop specifically includes:

[0015] The displacement and speed of each motor are measured in real time by an encoder installed inside the motor.

[0016] Calculate the synchronization error of each motor based on its displacement and speed;

[0017] The synchronization error is used as a feedback term in the external feedback loop.

[0018] When calculating synchronization error, the displacement and speed of each motor can be measured in real time by an encoder installed in the motor. By comparing the displacement and speed of each motor, the synchronization error of each motor can be calculated.

[0019] In some implementations, the method further includes: presetting the control parameters of the external feedback loop;

[0020] The synchronization error includes synchronization displacement error and synchronization velocity error;

[0021] The control parameters of the external feedback loop include a first parameter corresponding to the synchronous displacement error and a second parameter corresponding to the synchronous velocity error.

[0022] Specifically, synchronization errors include synchronization displacement errors and synchronization speed errors, used to ensure the synchronization of the displacement and speed of each motor, respectively. During control, it is also necessary to preset a first parameter corresponding to the synchronization displacement error and a second parameter corresponding to the synchronization speed error in order to adjust the motor output force. The magnitudes of the first and second parameters can be adjusted according to the actual situation of multiple motors, and are not restricted here.

[0023] In some implementations, using the output force error of each motor as the feedback term of the internal feedback loop specifically includes:

[0024] The deformation of the springs installed at the moving ends of each motor is measured in real time to obtain the actual output force of each motor.

[0025] Based on the actual output force of each motor and the corresponding expected sub-force, the output force error of each motor is calculated, and the output force error is used as the feedback term of the internal feedback loop.

[0026] When calculating the output force error, the actual output force of each motor can be obtained by measuring the deformation of the springs installed at the moving ends of each motor in real time. Then, the actual output force of each motor is compared with the corresponding expected force to obtain the output force error of each motor.

[0027] In addition, by installing springs in series at the moving end of the motor actuator, the output force of the motor can be accurately measured by measuring the deformation of the springs. On the other hand, the series springs provide a certain amount of redundancy for synchronization error of the entire device, which can reduce mechanical stress and deformation and help protect the equipment.

[0028] In some implementations, it also includes:

[0029] The control parameters of the internal feedback loop are preset.

[0030] In some implementations, the inner feedback loop is updated at a first preset frequency, and the outer feedback loop is updated at a second preset frequency.

[0031] The first preset frequency is greater than the second preset frequency.

[0032] In some embodiments, the inner feedback loop is provided with a first preset bandwidth, and the outer feedback loop is provided with a second preset bandwidth.

[0033] The first preset bandwidth is greater than the second preset bandwidth.

[0034] In addition, the present invention also provides a multi-motor synchronous force control system based on the above-mentioned multi-motor synchronous force control method, comprising:

[0035] On the table;

[0036] A base plate is disposed opposite to the upper platform, and several motors are fixedly installed on the side of the base plate facing the upper platform;

[0037] The motor is equipped with an encoder, and the moving ends of the motor's actuator are all connected to the upper platform via springs.

[0038] Displacement sensors for measuring the deformation of the springs are provided on the sides of each spring.

[0039] In implementing the multi-motor synchronous force control method described above, an upper platform and a base plate are set up. The upper platform serves as the driving surface for the multiple motors, and the motors are fixed between the base plate and the upper platform. The motors are equipped with encoders that can measure the displacement and speed of each motor in real time. The moving ends of the motor actuators are all connected to the upper platform via springs. Displacement sensors for measuring spring deformation are set on the side of the springs. By setting up springs, on the one hand, the output force of the motors can be accurately measured by measuring the spring deformation, and on the other hand, a certain amount of synchronization error redundancy can be provided to the entire device to reduce the mechanical stress and deformation of the equipment.

[0040] In some embodiments, guide holes are provided at the four corners of the upper platform, and guide rods matching the guide holes are provided at the four corners of the top surface of the base plate.

[0041] In some implementations, several motors are evenly distributed and are of the same model.

[0042] The multi-motor synchronous force control method and system provided by this invention have at least the following beneficial effects:

[0043] (1) By obtaining the total expected force of multiple motors and the characteristics of each motor, the sub-expected force of each motor can be calculated. At the same time, when each motor is controlled to run according to the corresponding sub-expected force, by setting up external feedback loop and internal feedback loop, and using the synchronization error of each motor as the feedback item of the external feedback loop and the output force error of each motor as the feedback item of the internal feedback loop, precise force control can be achieved in a limited space, and the synchronization of the movement of multiple motors can be guaranteed, which can meet more industrial needs.

[0044] (2) By installing springs in series at the end of the moving end of the motor actuator, the output force of the motor can be accurately measured by measuring the deformation of the springs. On the other hand, the series springs provide a certain amount of redundancy for the synchronization error of the whole device, which can reduce mechanical stress and deformation and is beneficial to protect the equipment. Attached Figure Description

[0045] The preferred embodiments will now be described in a clear and easy-to-understand manner, with reference to the accompanying drawings, to further explain the above-mentioned characteristics, technical features, advantages, and implementation methods of this solution.

[0046] Figure 1 This is a schematic diagram of the overall process of an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the control logic of an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the overall control loop according to an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of a single motor control circuit according to an embodiment of the present invention;

[0050] Figure 5 This is a Simulink simulation model diagram of an embodiment of the present invention;

[0051] Figure 6 This is a schematic diagram of the actual output force curves of each motor in an embodiment of the present invention;

[0052] Figure 7 This is a schematic diagram of the displacement curves of each motor in an embodiment of the present invention;

[0053] Figure 8 This is a schematic diagram of the displacement synchronization error curves of each motor in an embodiment of the present invention;

[0054] Figure 9 This is a schematic diagram of the system structure according to an embodiment of the present invention.

[0055] The numbers in the diagram are: 1-upper platform; 2-base plate; 3-motor; 4-actuator; 5-spring; 6-displacement sensor; 7-guide rod. Detailed Implementation

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0057] To keep the drawings concise, only the parts relevant to the invention are shown schematically in each figure, and they do not represent the actual structure of the product. Furthermore, for ease of understanding, in some figures, only one of components with the same structure or function is shown schematically, or only one is labeled. In this document, "one" can mean not only "only one" but also "more than one".

[0058] In one embodiment, refer to the accompanying drawings. Figure 1 and Figure 2 This invention provides a multi-motor synchronous force control method, including the following steps:

[0059] S1, Obtain the total expected force of multiple motors.

[0060] S2. Calculate the expected force of each motor based on the characteristics of each motor in the multi-motor system.

[0061] Based on the characteristics of each motor, the total expected force F is... d The force is allocated to each motor, and the desired force for each motor is F. di ,satisfy If the motors are of the same model, the expected force distributed among each motor should be similar. In this case, the sub-expected force of each motor can be set to F. di =F d / N.

[0062] S3. Set up an external feedback loop to control each motor to run according to the corresponding desired force, and use the synchronization error of each motor as the feedback item of the external feedback loop.

[0063] Preferably, the synchronization error of each motor is used as the feedback term of the external feedback loop, specifically including:

[0064] The displacement and speed of each motor are measured in real time by encoders installed inside the motors.

[0065] Calculate the synchronization error of each motor based on its displacement and speed.

[0066] The synchronization error is used as the feedback term in the external feedback loop.

[0067] When calculating synchronization error, the displacement and speed of each motor can be measured in real time by an encoder installed in the motor. By comparing the displacement and speed of each motor, the synchronization error of each motor can be calculated.

[0068] Further preferred options include: preset control parameters for the external feedback loop.

[0069] Synchronization error includes synchronous displacement error and synchronous velocity error; the control parameters of the external feedback loop include a first parameter corresponding to the synchronous displacement error and a second parameter corresponding to the synchronous velocity error.

[0070] Specifically, synchronization errors include synchronization displacement errors and synchronization speed errors, used to ensure the synchronization of the displacement and speed of each motor, respectively. During control, it is also necessary to preset a first parameter corresponding to the synchronization displacement error and a second parameter corresponding to the synchronization speed error in order to adjust the motor output force. The magnitudes of the first and second parameters can be adjusted according to the actual situation of multiple motors, and are not restricted here.

[0071] like Figure 3 and Figure 4 As shown, considering the synchronization error of each motor, a circular synchronization error feedback loop is set as the external feedback loop. During multi-motor synchronous operation, the movements of each motor should be as consistent as possible. If the synchronization error is too large, it will cause mechanical damage to the guiding mechanism. To ensure synchronous operation of each motor, a synchronization error feedback term is added to the control loop of the i-th motor. Where, k xi and c xi These are the first and second parameters of the external feedback loop, respectively; e xi and These are the synchronous displacement error and the synchronous velocity error, respectively.

[0072]

[0073] Where, x i Let be the actual displacement of the i-th motor. Let be the actual speed of the i-th motor.

[0074] S4. Set up an internal feedback loop to control each motor to run according to the corresponding desired force, and use the output force error of each motor as the feedback item of the internal feedback loop.

[0075] Preferably, the output force error of each motor is used as the feedback term of the internal feedback loop, specifically including:

[0076] The deformation of the springs installed at the moving ends of each motor is measured in real time to obtain the actual output force of each motor.

[0077] Based on the actual output force and the corresponding expected sub-force of each motor, the output force error of each motor is calculated, and the output force error is used as the feedback term of the internal feedback loop.

[0078] When calculating the output force error, the actual output force of each motor can be obtained by measuring the deformation of the springs installed at the moving ends of each motor in real time. Then, the actual output force of each motor is compared with the corresponding expected force to obtain the output force error of each motor.

[0079] In addition, by installing springs in series at the moving end of the motor actuator, the output force of the motor can be accurately measured by measuring the deformation of the springs. On the other hand, the series springs provide a certain amount of redundancy for synchronization error of the entire device, which can reduce mechanical stress and deformation and help protect the equipment.

[0080] Further preferred options include: control parameters for a preset internal feedback loop.

[0081] Considering the motor output force error, a force feedback loop is set as the internal feedback loop. The output force error feedback term added to the i-th motor control loop is k. Pi e Fi +k Ii ∫e Fi dt, where k Pi and k Ii For the control parameters of the internal feedback loop; e Fi This represents the error between the actual output force and the control force of the motor.

[0082] The actual output force of each motor is obtained by measuring the spring deformation. Assume the control force of the i-th motor is F. i The actual detected output force is F oi Due to wear and tear from friction and other factors in the actuator, generally F oi <F i And F oi Precise measurement is usually difficult. This solution adds a custom spring (which is essentially linear within the motor's stroke range) to the end of each motor. By measuring the spring's deformation, more accurate information about the motor's output force F can be obtained. oi And feed it back to the inner feedback loop.

[0083] Based on the above steps, a schematic diagram of the overall control loop can be obtained, as shown below. Figure 3 As shown. At this point, the control equation for the i-th motor is: The control circuit for the i-th motor is as follows: Figure 4 As shown, the control equation for each motor consists of three parts:

[0084] (1) Expectation F di ;

[0085] (2) External feedback loop, synchronous error feedback terms of each motor

[0086] (3) Internal feedback loop, motor output force error feedback term k Pi e Fi +k Ii ∫e Fi dt.

[0087] When performing high-power force control output, by acquiring the total desired force of multiple motors and the characteristics of each motor, the sub-desired force of each motor can be calculated. At the same time, when controlling each motor to run according to its corresponding sub-desired force, by setting up external and internal feedback loops, and using the synchronization error of each motor as the feedback term of the external feedback loop and the output force error of each motor as the feedback term of the internal feedback loop, precise force control can be achieved in a limited space, while ensuring the synchronization of the movement of multiple motors, thus meeting more industrial needs.

[0088] Specifically, by distributing the expected force curve of each motor according to the total expected force and making each motor execute according to the expected force, precise control can be achieved, and the displacement and speed of each motor can be kept highly synchronized.

[0089] In addition, control is achieved through two loops. The inner loop is a high-speed force feedback loop, which designs the control rate based on the motor output force error to make the motor output the corresponding desired force. The outer loop is a low-speed motion synchronization error loop, which designs the control rate based on the differences in displacement and speed of each motor to further ensure that each motor keeps running synchronously.

[0090] In one embodiment, the inner feedback loop is updated at a first preset frequency, and the outer feedback loop is updated at a second preset frequency, wherein the first preset frequency is greater than the second preset frequency.

[0091] In one embodiment, the inner feedback loop is provided with a first preset bandwidth, and the outer feedback loop is provided with a second preset bandwidth, wherein the first preset bandwidth is greater than the second preset bandwidth.

[0092] Furthermore, to demonstrate the synchronicity, stability, and convergence of this synchronous force control method, it can be assumed that the motors are of the same model, the load is the same, and all control parameters are also set to be the same, i.e., k xi =k x ,c xi =c x ,k Pi =k P ,k Ii =k I Let i = 1, 2, ..., N, and the resultant force output by the N motors be:

[0093]

[0094] in, The actual output resultant force of N motors is determined by adjusting parameter k. P and k I This allows for fast and stable convergence.

[0095] Since it is assumed that all motors are of the same model and have the same load, the dynamic equation of the i-th motor is:

[0096]

[0097] Where m is the load mass (including the moment of inertia of the motor rotor); b is mainly viscous friction; and τ is mainly gravity and Coulomb friction.

[0098] After correction via the inner loop, the actual output force error of the motor can quickly approach zero (the control bandwidth of the inner feedback loop is generally above 1kHz, or even reaches tens of kHz), that is...

[0099] but

[0100]

[0101]

[0102] Subtracting the equation corresponding to the (i+1)th motor from the equation corresponding to the i-th motor in the formula yields...

[0103]

[0104] The N component equations of the above equation can be written in matrix form as follows:

[0105] in,

[0106]

[0107] Rewriting the equation in the form of a state equation, i.e. in,

[0108]

[0109] The prerequisite for stable convergence of the control loop is that matrix A has no eigenvalues ​​with positive real parts. The eigenvalue equation of matrix A can be rewritten as:

[0110] ms 2 +bs+h i (c x s+k x )=0,i=1,2,…,N-1,

[0111] This set of N quadratic complex coefficient equations (corresponding to the 2N eigenvalues ​​of the matrix) has only its complex coefficients changing, and their values ​​are:

[0112]

[0113] parameter h i The real part is greater than or equal to 0, so choose an appropriate parameter k. x and c xThis ensures that the real parts of the solutions to the N univariate quadratic complex coefficient equations are all non-negative, meaning that matrix A has no eigenvalues ​​with positive real parts, thus satisfying the stability requirements of the control system.

[0114] In one embodiment, three identical motors operate synchronously, each with the same actuator and a transfer function of K. m / (L m s+1), where K m =0.95,L m =0.01, load mass (including the moment of inertia of the motor rotor) m = 30kg, viscous friction b = 100N·s / m, gravity and Coulomb friction τ = 0.

[0115] The total expected power is F d =600sin(10πt), the inner loop control coefficient is k I =1000,k P =10, the outer loop control coefficient is k x =1500,c x =200.

[0116] The initial position and speed of each motor are: A simulation model was built in Simulink, such as Figure 5 As shown. The actual output force curves of each motor are as follows. Figure 6 As shown, the actual output force curves and desired force curves of each motor match very well. The displacement curves of each motor are shown below. Figure 7 As shown, the displacement synchronization error of each motor is as follows: Figure 8 As shown, after a short transition, this scheme can quickly reduce the synchronization error of each motor to zero, achieving the purpose of synchronous force control. Simulation results prove the feasibility and efficiency of the multi-motor synchronous force control device and method proposed in this scheme.

[0117] Additionally, please refer to the attached instruction manual. Figure 9 The present invention also provides a multi-motor synchronous force control system based on the above-mentioned multi-motor synchronous force control method, including an upper platform 1 and a base plate 2. The base plate 2 is arranged opposite to the upper platform 1, and a plurality of motors 3 are fixedly installed on the side of the base plate 2 facing the upper platform 1.

[0118] Preferably, several motors 3 are evenly distributed and have the same model.

[0119] An encoder is installed inside the motor 3, and the movable end of the actuator 4 of the motor 3 is connected to the upper platform 1 through spring 5; a displacement sensor 6 for measuring the deformation of the spring 5 is installed on the side of each spring 5.

[0120] In implementing the above-mentioned multi-motor synchronous force control method, an upper platform 1 and a base plate 2 are set up. The upper platform 1 serves as the driving surface for the multiple motors. The motor 3 is fixed between the base plate 2 and the upper platform 1. An encoder is installed inside the motor 3, which can measure the displacement and speed of each motor in real time. The movable ends of the actuator 4 of the motor 3 are all connected to the upper platform 1 through springs 5. A displacement sensor 6 for measuring the deformation of the spring 5 is set on the side of the spring 5. By setting the spring 5, on the one hand, the output force of the motor can be accurately measured by measuring the deformation of the spring 5. On the other hand, it can provide a certain amount of synchronization error redundancy for the entire device, so as to reduce the mechanical stress and deformation of the equipment.

[0121] In one embodiment, guide holes are provided at all four corners of the upper platform 1, and guide rods 7 matching the guide holes are provided at all four corners of the top surface of the base plate 2.

[0122] By setting guide holes and guide rods 7, the upper platform 1 can move along the guide rods 7 when multiple motors are running, thus preventing the upper platform 1 from shifting.

[0123] It should be noted that the above embodiments can be freely combined as needed. The above description is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synchronous force control of multiple motors, characterized in that, Including steps, Obtain the total expected force of multiple motors; Based on the characteristics of each motor in a multi-motor system, calculate the expected sub-force of each motor. An external feedback loop is set up to control each motor to operate according to the corresponding desired force, and the synchronization error of each motor is used as the feedback item of the external feedback loop. An internal feedback loop is set up to control each motor to operate according to the corresponding desired sub-force, and the output force error of each motor is used as the feedback item of the internal feedback loop. The use of the output force error of each motor as the feedback term of the internal feedback loop specifically includes: The deformation of the springs installed at the moving ends of each motor is measured in real time to obtain the actual output force of each motor. Based on the actual output force of each motor and the corresponding expected sub-force, the output force error of each motor is calculated, and the output force error is used as the feedback term of the internal feedback loop.

2. The multi-motor synchronous force control method according to claim 1, characterized in that, The use of the synchronization error of each motor as the feedback term of the external feedback loop specifically includes: The displacement and speed of each motor are measured in real time by an encoder installed inside the motor. Calculate the synchronization error of each motor based on its displacement and speed; The synchronization error is used as a feedback term in the external feedback loop.

3. The multi-motor synchronous force control method according to claim 2, characterized in that, Also includes: The control parameters of the external feedback loop are preset; The synchronization error includes synchronization displacement error and synchronization velocity error; The control parameters of the external feedback loop include a first parameter corresponding to the synchronous displacement error and a second parameter corresponding to the synchronous velocity error.

4. The multi-motor synchronous force control method according to claim 1, characterized in that, Also includes: The control parameters of the internal feedback loop are preset.

5. A multi-motor synchronous force control method according to any one of claims 1-4, characterized in that, The feedback signal of the inner feedback loop is updated at a first preset frequency, and the feedback signal of the outer feedback loop is updated at a second preset frequency. The first preset frequency is greater than the second preset frequency.

6. The multi-motor synchronous force control method according to claim 5, characterized in that, The feedback signal of the inner feedback loop has a first preset bandwidth, and the feedback signal of the outer feedback loop has a second preset bandwidth. The first preset bandwidth is greater than the second preset bandwidth.

7. A multi-motor synchronous force control system based on the multi-motor synchronous force control method according to any one of claims 1-6, characterized in that, include: On the table; A base plate is disposed opposite to the upper platform, and several motors are fixedly installed on the side of the base plate facing the upper platform; The motor is equipped with an encoder, and the moving ends of the motor's actuator are all connected to the upper platform via springs. Displacement sensors for measuring the deformation of the springs are provided on the sides of each spring.

8. A multi-motor synchronous force control system according to claim 7, characterized in that, The upper platform has guide holes at each of its four corners, and the bottom plate has guide rods at each of its four corners that match the guide holes.

9. A multi-motor synchronous force control system according to claim 7, characterized in that, Several motors are evenly distributed and are of the same model.

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