Eight-wheel omnidirectional motor driven mobile platform system and control method thereof

Abstract

The present invention relates to the field of drive wheel technology control, and more specifically, to an eight-wheel omnidirectional motor-driven mobile platform system and a control method thereof. The system comprises four wheel assemblies, each of which includes a left hub motor and a right hub motor. The left hub motor and the right hub motor are respectively connected to a left wheel and a right wheel, forming a wheel module. The left hub motor and the right hub motor are each connected to a direction angle sensor, which is connected to a DIR direction module. The DIR direction module is connected to a CAN data decoding module, which is connected to a main control module. The left hub motor is connected to a left Field Operation Control (FOC) software module via a left power drive module, and the right hub motor is connected to a right Field Operation Control (FOC) software module via a right power drive module. The system enables the entire mobile platform to advance according to the direction and speed reference values ​​initially set by the main control module. During the movement process, the system can continuously adjust the error as needed to achieve the direction and speed set by the main control module.

Description

Technical Field

[0001] The present invention relates to the field of driving wheel technology control, and in particular to an eight-wheel omnidirectional motor-driven mobile platform system and a control method thereof. Background Art

[0002] An automated guided vehicle (AGV) is a transport vehicle equipped with an automated guidance system, such as an electromagnetic or optical one, that can move materials along a prescribed path. However, AGVs have poor steering performance, such as being unable to navigate complex road conditions, making them unsuitable for practical applications.

[0003] In view of this, the present invention provides an eight-wheel omnidirectional motor-driven mobile platform system and a control method thereof. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies of the prior art and provide an eight-wheel omnidirectional motor-driven mobile platform system and a control method thereof.

[0005] In order to solve the above technical problems, the following technical solutions are adopted:

[0006] An eight-wheel omnidirectional motor-driven mobile platform system includes four wheel assemblies. The wheel assemblies have the same structure, and all four wheel assemblies include a left hub motor, a right hub motor, a left power drive module, a right power drive module, a left FOC software module, and a right FOC software module. The left hub motor and the right hub motor are respectively connected to the left wheel and the right wheel, and the left wheel and the right wheel form a wheel module. The left hub motor and the right hub motor are both connected to a direction angle sensor, and the direction angle sensor is connected to a DIR direction module, and the DIR direction module is connected to a CAN data decoding module, and the CAN data decoding module is connected to a main control module. The left hub motor is connected to the left power drive module, and the left power drive module is connected to the left FOC software module. The right hub motor is connected to the right power drive module, and the right power drive module is connected to the right FOC software module. The left FOC software module and the right FOC software module are both connected to a CAN data decoding module.

[0007] A steering control method for an eight-wheel omnidirectional motor-driven mobile platform system includes the following steps:

[0008] (1) The CAN data decoding module transmits and decodes the direction reference value DIR.ref and speed reference value SP.ref(all) of the wheel module to the main control module. Then, the direction feedback value DIR.fback of the first set of wheel modules is obtained through the direction angle sensor. Finally, the direction error value DIR.err of the wheel module is obtained through the above direction reference value DIR.ref and direction feedback value DIR.fback.

[0009] (2) By adjusting the speed PI of the left FOC software module and the right FOC software module, the rotation speeds of the left wheel and the right wheel are adjusted respectively, and the left speed reference SP.ref(L) of the left wheel and the right speed reference SP.ref(R) of the right wheel are obtained again.

[0010] (3) First, the actual left wheel feedback speed SP.fback(L) and the actual right wheel feedback speed SP.fback(L) of the left wheel are transmitted to the left FOC software module and the right FOC software module through the rotor position encoder of the left hub motor and the rotor position encoder of the right hub motor, respectively, so as to obtain the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel.

[0011] (4) Repeat steps (2) and (3) until the left wheel speed error SP.err (L) of the left wheel and the right wheel speed error SP.err (R) of the right wheel are both zero, so that the direction deviation value DIR.err = 0. Finally, the left wheel and the right wheel move forward in the specified direction at the same speed.

[0012] (5) According to the above steps (1) to (4), adjust the wheels of the other three groups of wheel modules so that the mobile platform rotates in the set direction.

[0013] Furthermore, in step (1), when the reference mode of the wheel module pointing to the main control module is set, the direction angle sensor outputs a direction feedback value DIR.fback=0. When the direction of the wheel module deviates to the left of the 0 point, DIR.fback is a negative number, and when the direction deviates to the right of the 0 point, DIR.fback is a positive number.

[0014] Furthermore, in step (1), the calculation formula of the direction error value DIR.err of the wheel module is as follows.

[0015] DIR.err = DIR.ref - DIR.fback.

[0016] If the direction error value DIR.err is zero, it reflects that the wheel direction of the current wheel module is moving normally.

[0017] If the direction error value DIR.err is a positive number, it reflects that the wheel of the current wheel module is deviating to the left.

[0018] If the direction error value DIR.err is a negative number, it reflects that the wheel of the current wheel module is deviating to the right.

[0019] Furthermore, in step (2), the calculation formulas of the left speed reference SP.ref(L) of the left wheel and the right speed reference SP.ref(R) of the right wheel are as follows:

[0020] SP.ref(L) = SP.ref(all) + DIR.err * kp +Σ(DIR.err * ki);

[0021] SP.ref(R) = SP.ref(all) - DIR.err * kp -Σ(DIR.err * ki);

[0022] Among them, kp and ki are the speed PI adjustment coefficients of the left FOC software module and the right FOC software module;

[0023] Furthermore, in step (3), the left wheel speed error SP.err (L) of the left wheel and the right wheel speed error SP.err (R) of the right wheel are calculated as follows:

[0024] SP.err(L)=SP.ref(L)-SP.fback(L);

[0025] SP.err(R)=SP.ref(R)-SP.fback(R);

[0026] By comparing the difference between the left speed reference SP.ref(L) and the left wheel feedback speed SP.fback(L), and the difference between the right speed reference SP.ref(R) and the right wheel feedback speed SP.fback(R), the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel are respectively obtained.

[0027] Furthermore, in step (3), the left wheel speed error SP.err (L) and the right wheel speed error SP.err (R) are respectively adjusted by the speed PI of the left FOC software module and the right FOC software module to obtain the IQ current reference values ​​of the left hub motor and the right hub motor, and the formula is as follows:

[0028] IQ.ref(L) = SP.err (L) * kp + Σ(SP.err (L) * ki); IQ.ref(L) is the IQ current reference value of the left hub motor;

[0029] IQ.ref(R) = SP.err (R) * kp +Σ(SP.err (R) * ki); IQ.ref(R) is the IQ current reference value of the right hub motor.

[0030] Furthermore, in step (4), the left speed reference SP.ref(L) of the left wheel and the right speed reference SP.ref(R) of the right wheel are readjusted by the IQ current reference value of the left hub motor and the IQ current reference value of the right hub motor until the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel are both zero, thereby making the direction deviation value DIR.err=0, and finally the left wheel and the right wheel move forward in the specified direction at the same speed.

[0031] The above technical solution has the following beneficial effects:

[0032] The present invention provides an eight-wheel omnidirectional motor-driven mobile platform system and its control method. The control method first sets up four wheel assemblies on the mobile platform, each wheel assembly having two wheels, forming a differential wheel structure. Each wheel is equipped with a corresponding power drive module and FOC software module. The CAN data decoding module then transmits and decodes the wheel module's direction reference value DIR.ref and speed reference value SP.ref(all) from the main control module. These values ​​are then compared with the direction feedback value DIR.fback obtained by the direction angle sensor. If the two values ​​are not equal, it indicates that the direction of the wheel module in the group has deviated. The left and right FOC software modules then continuously adjust the left speed reference SP.ref(L1) of the left wheel and the right speed reference SP.ref(R1) of the right wheel, ultimately reducing the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel to zero, thereby achieving a direction deviation value DIR.err=0. Finally, the left and right wheels move at the same speed in the specified direction. At the same time, if there is a directional error in the other three sets of wheels, the above method is also followed, so that the entire mobile platform moves forward according to the direction reference value DIR.ref and speed reference value SP.ref(all) initially set by the main control module. The movement process can continuously adjust the error as needed to achieve the direction and speed set by the main control module to complete the movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the accompanying drawings:

[0034] Figure 1 Schematic diagram of the structure of an eight-wheel omnidirectional motor-driven mobile platform system according to an embodiment of the present invention.

[0035] Figure 2 This is a structural diagram of the mobile platform moving forward according to an embodiment of the present invention.

[0036] Figure 3 This is a structural diagram of the mobile platform turning left according to an embodiment of the present invention.

[0037] Figure 4 This is a structural diagram of the left straight moving platform according to an embodiment of the present invention.

[0038] Figure 5 This is a structural diagram of a mobile platform rotating in place according to an embodiment of the present invention.

[0039] Figure 6 This is a structural diagram of the mobile platform according to the embodiment of the present invention, which moves at a certain angle with the chassis. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. However, it should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the present invention.

[0041] See Figure 1-6 An eight-wheel omnidirectional motor-driven mobile platform system includes four wheel assemblies, each having the same structure, and each of the four wheel assemblies includes a left hub motor, a right hub motor, a left power drive module, a right power drive module, a left FOC software module, and a right FOC software module. The left hub motor and the right hub motor are respectively connected to the left wheel and the right wheel, and the left wheel and the right wheel form a wheel module. The left hub motor and the right hub motor are both connected to a direction angle sensor, the direction angle sensor is connected to a DIR direction module, the DIR direction module is connected to a CAN data decoding module, the CAN data decoding module is connected to a main control module, the left hub motor is connected to the left power drive module, the left power drive module is connected to the left FOC software module, the right hub motor is connected to the right power drive module, the right power drive module is connected to the right FOC software module, and the left FOC software module and the right FOC software module are both connected to the CAN data decoding module.

[0042] As a further explanation of the present invention, the four sets of wheel assemblies are all differential drive assemblies, the differential drive assembly includes a left wheel and a right wheel, a left transmission unit can be set between the left wheel and the left hub motor, and a right transmission unit can be set between the right wheel and the right hub motor. The above-mentioned connection of the differential drive assembly is connected to a fixed plate, the upper part of the fixed plate is connected to a rotating shaft, and the upper part of the rotating shaft is connected to the chassis of the mobile platform.

[0043] Based on the above mobile platform, the present invention also discloses a steering control method for an eight-wheel omnidirectional motor-driven mobile platform system, comprising the following steps:

[0044] (1) For different motion modes, the direction reference value DIR.ref and speed reference value SP.ref(all) of each group of wheel modules may be the same or different. For example Figure 3 Turn left, Figure 5 At this time, the direction reference value DIR.ref and speed reference value SP.ref(all) of each group of wheel modules are different. The following is an example of one group of wheel modules.

[0045] First, the CAN data decoding module transmits and decodes the direction reference value DIR.ref and speed reference value SP.ref(all) for the first set of wheel modules from the main control module. Then, the direction feedback value DIR.fback for the first set of wheel modules is obtained via the direction angle sensor. Finally, the direction error value DIR.err of the wheel module is obtained using the direction reference value DIR.ref and direction feedback value DIR.fback. Through this method, the direction error value DIR.err of the wheel group is first obtained, and the overall direction error of the wheel assembly is adjusted in the following steps.

[0046] Specifically, in step (1), when the reference mode of the wheel module pointing to the main control module is set, the direction angle sensor outputs a direction feedback value DIR.fback=0. When the direction of the wheel module deviates to the left of the 0 point, DIR.fback is a negative number, and when the direction deviates to the right of the 0 point, DIR.fback is a positive number.

[0047] Specifically, in step (1), the calculation formula of the direction error value DIR.err of the wheel module is as follows:

[0048] DIR.err = DIR.ref - DIR.fback.

[0049] If the direction error value DIR.err is zero, it reflects that the wheel direction of the current wheel module is moving normally.

[0050] If the direction error value DIR.err is a positive number, it reflects that the wheel of the current wheel module is deviating to the left.

[0051] If the direction error value DIR.err is a negative number, it reflects that the wheel of the current wheel module is deviating to the right.

[0052] (2) By adjusting the speed PI of the left FOC software module and the right FOC software module, the rotation speeds of the left wheel and the right wheel are adjusted respectively, and the left speed reference SP.ref(L) of the left wheel and the right speed reference SP.ref(R) of the right wheel are obtained again.

[0053] Specifically, in step (2), when the direction reference value DIR.ref minus the direction feedback value DIR.fback equals the direction error value DIR.err, DIR.err is a positive number, which reflects that the current wheel is deviating to the left. At this time, the speed reference value SP.ref(all) is added to the direction deviation value DIR.err to form the left speed reference SP.ref(L), which is the currently adjusted left wheel set speed. Similarly, the speed reference value SP.ref(all) is subtracted from the upper direction deviation value DIR.err to form the right speed reference SP.ref(R), which is the currently adjusted right wheel set speed. This will make the left wheel faster than the right wheel, correcting the right turn and reducing the deviation. Of course, in order to stabilize the direction control, this process refers to PI adjustment to achieve faster and more stable direction control. In this way, the left speed reference SP.ref(L) and the right speed reference SP.ref(R) of the right wheel are continuously adjusted until the direction deviation value DIR.err is zero, and the adjustment is completed.

[0054] Specifically, the calculation formulas for the left speed reference SP.ref(L) of the left wheel and the right speed reference SP.ref(R) of the right wheel are as follows:

[0055] SP.ref(L) = SP.ref(all) + DIR.err * kp +Σ(DIR.err * ki);

[0056] SP.ref(R) = SP.ref(all) - DIR.err * kp -Σ(DIR.err * ki);

[0057] Among them, kp and ki are the speed PI adjustment coefficients of the left FOC software module and the right FOC software module.

[0058] (3) First, the actual left wheel feedback speed SP.fback(L) and the actual right wheel feedback speed SP.fback(L) of the left wheel are transmitted to the left FOC software module and the right FOC software module through the rotor position encoder of the left hub motor and the rotor position encoder of the right hub motor, respectively, so as to obtain the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel.

[0059] In step (3), the left wheel speed error SP.err (L) of the left wheel and the right wheel speed error SP.err (R) of the right wheel are calculated as follows:

[0060] SP.err(L)=SP.ref(L)-SP.fback(L);

[0061] SP.err(R)=SP.ref(R)-SP.fback(R);

[0062] By comparing the difference between the left speed reference SP.ref(L) and the left wheel feedback speed SP.fback(L), and the difference between the right speed reference SP.ref(R) and the right wheel feedback speed SP.fback(R), the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel are respectively obtained.

[0063] In step (3), the left wheel speed error SP.err (L) and the right wheel speed error SP.err (R) are respectively adjusted by the speed PI of the left FOC software module and the right FOC software module to obtain the IQ current reference values ​​of the left hub motor and the right hub motor, and the formula is as follows:

[0064] IQ.ref(L) = SP.err (L) * kp + Σ(SP.err (L) * ki); IQ.ref(L) is the IQ current reference value of the left hub motor;

[0065] IQ.ref(R) = SP.err (R) * kp +Σ(SP.err (R) * ki); IQ.ref(R) is the IQ current reference value of the right hub motor.

[0066] Adjusting the directional error value DIR.err requires adjusting the left speed reference SP.ref(L) and the right wheel's right speed reference SP.ref(R). The adjustment of the left speed reference SP.ref(L) and the right wheel's right speed reference SP.ref(R) is based on the left wheel feedback speed SP.fback(L) and the right wheel feedback speed SP.fback(L). The left and right FOC software modules then determine the left wheel speed error SP.err(L) and the right wheel speed error SP.err(R). The left and right wheel speed errors SP.err(L) and SP.err(R) are then used to determine the IQ current reference values ​​for the left and right wheel hub motors.

[0067] (4) Repeat the above steps (2) and (3), continuously adjust the IQ current reference value of the left hub motor and the IQ current reference value of the right hub motor, and then continuously change the left speed reference SP.ref(L) and the right speed reference SP.ref(R) of the right wheel, until the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel are both zero, so that the direction deviation value DIR.err=0, and finally the left wheel and the right wheel move at the same speed in the specified direction.

[0068] Specifically, in step (4), the left speed reference SP.ref(L) of the left wheel and the right speed reference SP.ref(R) of the right wheel are readjusted by the IQ current reference value of the left hub motor and the IQ current reference value of the right hub motor until the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel are both zero, so that the direction deviation value DIR.err=0, and finally the left wheel and the right wheel move forward in the specified direction at the same speed.

[0069] (5) According to the above steps (1) to (4), adjust the wheels of the other three groups of wheel modules so that the mobile platform rotates in the set direction.

[0070] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications based on the present invention to solve substantially the same technical problems and achieve substantially the same technical effects are included within the scope of protection of the present invention.

Claims

1. An eight-wheel omnidirectional motor-driven mobile platform system includes four wheel assemblies with the same structure, characterized by: The four wheel assemblies each include a left hub motor, a right hub motor, a left power drive module, a right power drive module, a left FOC software module and a right FOC software module. The left hub motor and the right hub motor are respectively connected to the left wheel and the right wheel. The left wheel and the right wheel form a wheel module. The left hub motor and the right hub motor are both connected to a direction angle sensor, the direction angle sensor is connected to a DIR direction module, the DIR direction module is connected to a CAN data decoding module, the CAN data decoding module is connected to a main control module, the left hub motor is connected to the left power drive module, the left power drive module is connected to the left FOC software module, the right hub motor is connected to the right power drive module, the right power drive module is connected to the right FOC software module, and the left FOC software module and the right FOC software module are both connected to the CAN data decoding module.

2. The steering control method of the eight-wheel omnidirectional motor-driven mobile platform system according to claim 1, characterized in that The following steps are involved: (1) First, the direction reference value DIR.ref and the speed reference value SP.ref(all) of the first group of the wheel modules of the main control module are transmitted and decoded by the CAN data decoding module; then, the direction feedback value DIR.fback of the first group of the wheel modules is obtained by the direction angle sensor; finally, the direction error value DIR.err of the wheel module is obtained by the above-mentioned direction reference value DIR.ref and direction feedback value DIR.fback; (2) adjusting the speeds of the left and right wheels respectively through the speed PI regulation of the left FOC software module and the right FOC software module, and re-obtaining the left speed reference SP.ref(L) of the left wheel and the right speed reference SP.ref(R) of the right wheel; (3) First, the actual left wheel feedback speed SP.fback(L) and the actual right wheel feedback speed SP.fback(L) of the left wheel are transmitted to the left FOC software module and the right FOC software module through the rotor position encoder of the left hub motor and the rotor position encoder of the right hub motor, thereby obtaining the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel; (4) Repeat steps (2) and (3) until the left wheel speed error SP.err (L) of the left wheel and the right wheel speed error SP.err (R) of the right wheel are both zero, so that the direction deviation value DIR.err = 0, and finally the left wheel and the right wheel move forward in the specified direction at the same speed; (5) According to the above steps (1) to (4), adjust the wheels of the other three groups of wheel modules so that the mobile platform rotates in the set direction.

3. The steering control method of the eight-wheel omnidirectional motor-driven mobile platform system according to claim 2, characterized in that: In the step (1), when the reference mode of the wheel module pointing to the main control module is set, the direction angle sensor outputs a direction feedback value DIR.fback=0. When the direction of the wheel module deviates to the left of the 0 point, DIR.fback is a negative number, and when the direction deviates to the right of the 0 point, DIR.fback is a positive number.

4. The steering control method of the eight-wheel omnidirectional motor-driven mobile platform system according to claim 2 or 3, characterized in that: In step (1), the calculation formula of the direction error value DIR.err of the wheel module is as follows: DIR.err =DIR.ref-DIR.fback; If the direction error value DIR.err is zero, it reflects that the wheel direction of the current wheel module is moving normally; If the direction error value DIR.err is a positive number, it reflects that the wheel of the current wheel module is deviating to the left; If the direction error value DIR.err is a negative number, it reflects that the wheel of the current wheel module is deviating to the right.

5. The steering control method of the eight-wheel omnidirectional motor-driven mobile platform system according to claim 4, characterized in that: In step (2), the calculation formulas of the left speed reference SP.ref(1) of the left wheel and the right speed reference SP.ref(1) of the right wheel are as follows: SP.ref(L) = SP.ref(all) + DIR.err * kp +Σ(DIR.err * ki); SP.ref(R) = SP.ref(all) - DIR.err * kp -Σ(DIR.err * ki); Among them, kp and ki are the speed PI adjustment coefficients of the left FOC software module and the right FOC software module.

6. The steering control method of the eight-wheel omnidirectional motor-driven mobile platform system according to claim 5, characterized in that: In step (3), the left wheel speed error SP.err (L) of the left wheel and the right wheel speed error SP.err (R) of the right wheel are calculated as follows: SP.err(L)=SP.ref(L)-SP.fback(L); SP.err(R)=SP.ref(R)-SP.fback(R); By comparing the difference between the left speed reference SP.ref(L) and the left wheel feedback speed SP.fback(L), and the difference between the right speed reference SP.ref(R) and the right wheel feedback speed SP.fback(R), the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel are respectively obtained.

7. The steering control method of the eight-wheel omnidirectional motor-driven mobile platform system according to claim 6, characterized in that: In step (3), the left wheel speed error SP.err (L) and the right wheel speed error SP.err (R) are respectively adjusted by the speed PI of the left FOC software module and the right FOC software module to obtain the IQ current reference values ​​of the left hub motor and the right hub motor, and the formula is as follows: IQ.ref(L) = SP.err (L) * kp + Σ(SP.err (L) * ki); IQ.ref(L) is the IQ current reference value of the left hub motor; IQ.ref(R) = SP.err (R) * kp +Σ(SP.err (R) * ki); IQ.ref(R) is the IQ current reference value of the right hub motor.

8. The steering control method of the eight-wheel omnidirectional motor-driven mobile platform system according to claim 7, characterized in that: In step (4), the left speed reference SP.ref(L) of the left wheel and the right speed reference SP.ref(R) of the right wheel are readjusted by the IQ current reference value of the left hub motor and the IQ current reference value of the right hub motor until the left wheel speed error SP.err(L) of the left wheel and the right wheel speed error SP.err(R) of the right wheel are both zero, so that the direction deviation value DIR.err=0, and finally the left wheel and the right wheel move forward in the specified direction at the same speed.

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