CN101885351B - Split-type differential drive device and omnibearing movable automatic guided vehicle thereof - Google Patents

Abstract

The invention discloses a split-type differential drive device and an omnibearing movable automatic guided vehicle thereof, belonging to the field of an automatic conveying device. The device is provided with an upper rotating disc which is fixed on a vehicle body and is assembled together with a lower rotating disc in a coaxial way by a thrust bearing; the upper rotating disc is provided with an angle sensor and an electromagnetic clutch; and the lower rotating disc is provided with a guide sensor, a vehicle controller and two sets of wheel type moving device, each of which comprises a motor driver, an motor brake, a servo motor, a rotary encoder, a speed reducer and a driving wheel. The device of the invention has the advantages of simple structure, high bearing capacity, accurate control, stable running and the like; and the method fully utilizes the characteristics of the device, is simple in control principle and good in path adaptability, and has higher stability, accuracy and rapidity.

Description

Split type differential driving device and all-directional moving automatic guided vehicle thereof

Technical Field

The invention relates to a separable differential driving device and an all-directional mobile automatic guided vehicle thereof, belonging to the field of automatic conveying equipment.

Background

The driving/steering device is a motion executing mechanism of a wheeled electric vehicle, and according to the degree of freedom of planar motion, an Automatic Guided Vehicle (AGV) has an incomplete moving mode with limited lateral motion and an all-directional moving mode capable of realizing all planar motion. The all-directional moving automatic guided vehicle can not only longitudinally advance and retreat along the vehicle body and rotate around the center of the vehicle body in situ, but also transversely move leftwards and rightwards along the vehicle body, can move along any direction in a plane while keeping the posture of the vehicle body unchanged, and has good maneuverability on limited operation space.

An omnidirectional Wheel represented by a Mecanum Wheel (Mecanum Wheel) and a spherical Wheel can rotate around a main shaft to realize forward and backward movement, and can also generate lateral motion along the direction of the main shaft, so that the omnidirectional Wheel is a technical scheme for realizing an omnidirectional moving mode. The other technical scheme is that an all-directional movement mode is realized through a special layout of conventional wheels, for example, a layout of a pair of double-steering driving wheels with directions controlled by a steering motor and rotating speeds controlled by a driving motor is adopted, however, a control system of the scheme is complex, and the steering synchronism of two wheels controlled independently is poor.

In order to improve the synchronism of the steering control of the two wheels, a driving/steering mechanism (patent number: ZL200620028342.5) of the automatic guided vehicle is used for driving and connecting a motor and a speed reducer through a steering positioning mechanism, the output end of the speed reducer is in driving connection with a through shaft, and two driving wheels are in clutch type driving connection with two ends of the through shaft by adopting an electromagnetic clutch. An upper rotary disc of the steering positioning mechanism is fixed on the shell of the motor, and a lower rotary disc is fixed on the shell of the speed reducer; detecting a relative rotation angle between the upper rotary table and the lower rotary table through an angle sensor, and correcting the zero position of the angle sensor by using a middle position switch and a positioning pit; the positioning pin is driven by the electromagnet of the upper turntable to sink into the positioning pit of the lower turntable, so that the upper turntable and the lower turntable are locked. The device can ensure the synchronism of the two-wheel steering control, but has the following defects: (1) the motion state of the driving wheel is difficult to be accurately controlled through clutch type friction driving; the device takes the shell of the motor and the speed reducer as a main bearing structure, and the limited strength and rigidity are not suitable for the large-load working condition; (3) the upper turntable and the lower turntable are difficult to be accurately locked at any angle by utilizing the connection mode of the positioning pin and the positioning pit; (4) the angle sensor needs a middle position switch to perform centering calibration; (5) the structure of the electromagnetic clutch of the driving wheel in the device is complex.

Because the McCaram wheel and the spherical wheel can realize all plane motions, the all-direction moving automatic guided vehicle adopting the wheels is not restricted by incompleteness, the motion control method is relatively simple, but the all-direction wheels have complicated mechanical structure and high manufacturing cost, and have difficult adaptivity to the shape change of a running path. The automatic guided vehicle adopting the conventional wheels cannot directly eliminate the lateral position deviation due to incomplete constraint, the lateral position deviation needs to be indirectly eliminated by utilizing the longitudinal displacement of the vehicle body in motion control, the motion control method is relatively complex, and a large motion space is needed.

Disclosure of Invention

The invention aims to provide a separable differential driving device which has simple structure, large bearing capacity, accurate control and stable operation; the characteristics of the device are fully utilized, and a motion control method which has simple control principle, good path adaptability, higher stability, accuracy and rapidness is provided for the all-directional mobile automatic guided vehicle.

A separable differential driving device of a wheeled electric vehicle is characterized by comprising an upper turntable and a lower turntable, wherein the upper turntable is provided with a central hole, and the upper end surface of the lower turntable is provided with a central shaft; the central hole of the upper turntable and the central shaft of the lower turntable are coaxially assembled through a thrust bearing; a cylindrical electromagnetic clutch is also arranged between the central hole of the upper turntable and the central shaft of the lower turntable; two sets of wheel type moving devices are symmetrically arranged on the lower turntable along two sides of the central shaft, the right wheel type moving device comprises a right motor driver, a right motor brake, a right servo motor, a right rotary encoder, a right speed reducer and a right driving wheel, and the left wheel type moving device comprises a left motor driver, a left motor brake, a left servo motor, a left rotary encoder, a left speed reducer and a left driving wheel; the lower turntable is also provided with a guide sensor for detecting the path deviation and a vehicle-mounted controller for realizing autonomous driving; the guide sensor, the right rotary encoder and the left rotary encoder are connected with the vehicle-mounted controller through a signal input circuit; the vehicle-mounted controller is respectively connected with the right motor driver, the left motor driver, the right motor brake and the left motor brake through the signal output circuit; the upper turntable is provided with an angle sensor for detecting the rotating angle between the upper turntable and the lower turntable, the shell of the angle sensor is fixed on the upper end surface of the upper turntable, and the rotor of the angle sensor is mechanically connected with the central shaft of the lower turntable and is connected with the vehicle-mounted controller on the lower turntable through a signal input circuit.

The specific installation mode of the electromagnetic clutch is as follows: the casing of the electromagnetic clutch is fixed in the central hole of the upper turntable, and whether the electromagnetic coil is electrified or not is controlled by the driving circuit of the vehicle-mounted controller, and clutch type mechanical connection is carried out between the friction blocks which are uniformly distributed in the circumferential direction and the central shaft of the lower turntable.

An omni-directional mobile automated guided vehicle using the above-described separable differential drive apparatus, characterized in that: the separable differential driving device is arranged in the center below the vehicle body, the upper turntable of the separable differential driving device is in rigid fixed connection or flexible suspension connection with the vehicle body, and the upper turntable and the vehicle body do not move relatively in the horizontal direction; at least 2 free wheels are arranged on the periphery below the vehicle body, and the moving speed and the moving direction of the free wheels depend on the moving state of the vehicle body; a control storage battery pack for supplying power to the angle sensor, the right rotary encoder, the left rotary encoder, the guide sensor and the vehicle-mounted controller is also arranged on the vehicle body; and a storage battery pack for supplying power to drive the electromagnetic clutch, the right motor brake, the left motor brake, the right motor driver and the left motor driver is also arranged on the vehicle body.

The all-directional moving working principle of the automatic guided vehicle is as follows: the vehicle-mounted controller independently controls the two servo motors through the two motor drivers respectively, and then independently drives the two driving wheels through the two speed reducers respectively, the movement speed and the direction of each driving wheel can be independently and accurately controlled, and the speed difference between the two driving wheels can enable the lower turntable to move along the circular arc track. The vehicle-mounted controller controls the connection state between the lower turntable and the vehicle body through the electromagnetic clutch, when the lower turntable and the vehicle body are not locked, the two driving wheels are set to have equal speed and opposite directions, the movement direction of the lower turntable is freely adjusted through the in-situ rotation around the central shaft, and the movement direction angle of the lower turntable is detected in real time through the angle sensor; when the motion direction angle reaches the given value, the vehicle-mounted controller stops the servo motor and immediately brakes through the motor brake, and then locks the lower turntable and the vehicle body to keep the motion directions of the lower turntable and the vehicle body consistent. Therefore, the automatic guided vehicle can realize the all-directional movement along any direction angle while keeping the posture of the vehicle body unchanged.

Compared with the prior driving/steering device, the device has the following advantages: (1) the structure is simple. The invention adopts the modular structure of the upper turntable, the lower turntable and the wheel type moving device thereof, and has simple structure, low manufacturing cost and good maintainability. (2) The bearing capacity is large. The main bearing structures adopted by the invention are a circular truncated cone-shaped upper turntable and a lower turntable, the central hole of the upper turntable and the central shaft of the lower turntable are coaxially assembled through a thrust bearing, and the whole device has enough strength and rigidity and can be suitable for large-load working conditions. (3) The control is accurate. The invention respectively controls the movement speed and direction of the two driving wheels independently and accurately through the two sets of motor drivers and the servo motor, and can form effective speed difference to realize the steering control of the lower turntable and even the vehicle body; according to the invention, the electromagnetic clutch in the central hole of the upper turntable drives the friction block to press the central shaft of the lower turntable, so that the upper turntable and the lower turntable can be accurately locked at any angle; the absolute rotary encoder is used as the angle sensor, zero point calibration is not required to be carried out by an external device, and the rotating angle between the upper turntable and the lower turntable can be accurately measured. (4) The operation is stable. According to the bearing capacity of the automatic guided vehicle, the upper turntable and the vehicle body are in rigid fixed connection or flexible suspension connection, so that effective contact between the driving wheel and the ground is ensured to generate enough driving force.

The path self-adaptive tracking control method of the automatic guided vehicle is characterized by comprising the following steps: adopts a self-adaptive tracking control method aiming at the running paths with different shapes,

the method I is characterized in that the stability of the movement of the vehicle body is improved through a free state tracking control method, and the specific method comprises the following steps: the locking between the lower turntable and the vehicle body is released through an electromagnetic clutch in the separable differential driving device; the guide sensor detects the path deviation between the lower turntable and the ground guide marking and sends the path deviation to the vehicle-mounted controller; the vehicle-mounted controller accurately controls the speed difference between the right driving wheel and the left driving wheel through the right servo motor and the left servo motor respectively, so that the lower turntable can quickly adjust the position and the posture of the lower turntable along with the shape change of the running path; the vehicle body is not directly used for tracking the shape change of the running path, but is driven by the tracking motion of the lower turntable and rotates around the central shaft of the lower turntable relatively;

the second method is to precisely adjust the position and the posture of the vehicle body by an omnibearing tracking control method, and the specific method is as follows: the method is characterized in that the path deviation of the automatic guided vehicle is eliminated along any movement direction while the posture of the vehicle body is kept unchanged, and the method specifically comprises the following three steps:

firstly, stopping the automatic guided vehicle, and unlocking a lower turntable and a vehicle body through an electromagnetic clutch in a separable differential driving device; the guide sensor detects the path deviation between the vehicle body and the ground guide marking and sends the path deviation to the vehicle-mounted controller; the vehicle-mounted controller calculates the motion direction angle of the automatic guided vehicle according to the motion direction angle, and further calculates the rotation direction and angle of the lower rotary table relative to the vehicle body; the vehicle-mounted controller respectively controls the two driving wheels to rotate in the forward direction and the reverse direction through the right servo motor and the left servo motor, and the speeds of the two driving wheels are kept to be the same; the lower turntable rotates around the central shaft of the lower turntable in a preset direction, and the vehicle-mounted controller detects the rotation angle between the lower turntable and the vehicle body in real time through the angle sensor; when the rotating angle reaches a preset moving direction angle, the vehicle-mounted controller stops the right servo motor and the left servo motor, the right servo motor brake and the left servo motor brake immediately brake, and the lower rotary disc stops rotating;

locking the lower turntable and the vehicle body through an electromagnetic clutch in the separable differential driving device; the guide sensor detects the path deviation between the vehicle body and the ground guide marking and sends the path deviation to the vehicle-mounted controller; the vehicle-mounted controller) calculates the motion trail of the automatic guided vehicle according to the path deviation; accurately controlling the speed of the right driving wheel and the left driving wheel through the right servo motor and the left servo motor, and enabling the automatic guided vehicle to approach the ground guide marking line through a proper geometric track according to the movement direction set in the step one so as to eliminate the path deviation of the vehicle body;

stopping the automatic guided vehicle, and releasing the locking between the lower turntable and the vehicle body through an electromagnetic clutch in the separable differential driving device; the vehicle-mounted controller calculates the rotating direction and angle of the lower turntable relative to the vehicle body according to the existing posture of the vehicle body; the vehicle-mounted controller respectively controls the two driving wheels to rotate in the forward direction and the reverse direction through the right servo motor and the left servo motor, and the speeds of the two driving wheels are kept to be the same; the lower turntable rotates around the central shaft thereof in a preset direction, and the vehicle-mounted controller detects whether the self direction of the lower turntable is superposed with the vehicle body in real time through the angle sensor; when the self direction of the lower rotary disc is recovered to be coincident with the vehicle body, the vehicle-mounted controller stops the right servo motor and the left servo motor, the right servo motor brake and the left servo motor brake are used for immediately braking, and the lower rotary disc stops rotating; finally, the lower turntable and the vehicle body are locked through an electromagnetic clutch in the separable differential driving device;

the self-adaptive tracking control method further comprises a third method, wherein the third method is used for realizing the rapid movement of the vehicle through a locking state tracking control method, and the specific method is as follows: the lower turntable and the vehicle body are locked by an electromagnetic clutch in the separable differential driving device; the guide sensor detects the path deviation between the vehicle body and the ground guide marking and sends the path deviation to the vehicle-mounted controller; the vehicle-mounted controller adopts multi-step prediction optimal control or single-step prediction intelligent control aiming at different direction angle deviations, eliminates the path deviation of the automatic guided vehicle by adjusting the speed difference between two driving wheels, and sets the target speed of motor servo control according to the speed difference control quantity generated by tracking control.

When the deviation of the direction angle is not more than 5 degrees, the multi-step prediction optimal control adopts a kinematic model to calculate a multi-step control quantity sequence with optimal deviation rectification coordination, namely

<math><mrow> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <mo>-</mo> <mfrac> <mrow> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> </mrow> <mrow> <mn>2</mn> <mi>N</mi> <mfrac> <msub> <mi>T</mi> <mi>s</mi> </msub> <mi>W</mi> </mfrac> </mrow> </mfrac> <mo>+</mo> <mn>3</mn> <mrow> <mo>(</mo> <mi>k</mi> <mo>-</mo> <mfrac> <mrow> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow> <mn>2</mn> </mfrac> <mo>)</mo> </mrow> <mo>[</mo> <mfrac> <mrow> <mi>Nv</mi> <msub> <mi>T</mi> <mi>s</mi> </msub> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> <mo>-</mo> <mn>2</mn> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> </mrow> <mrow> <mrow> <mo>(</mo> <msup> <mi>N</mi> <mn>3</mn> </msup> <mo>-</mo> <mi>N</mi> <mo>)</mo> </mrow> <mfrac> <msub> <mi>T</mi> <mi>s</mi> </msub> <mi>W</mi> </mfrac> <mi>v</mi> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> </mfrac> <mo>]</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow></math>

Synchronously and accurately eliminating the deviation of the two paths; wherein e is_θ(0) And e_d(0) The direction angle deviation and the lateral distance deviation between the vehicle body and the ground guide marking line are detected by the guide sensor; t is_sIs the control period of the vehicle-mounted controller (31); w is the distance between the right and left drive wheels; v is the linear velocity of the center of the vehicle body; Δ v (k) is a speed difference control amount in the kth control period, where k is 0, 1, 2.N-1; n is the total step number of the control quantity sequence, and the value of N is the minimum integer value meeting the following constraint conditions:

<math><mrow> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msub> <mrow> <mo>|</mo> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>|</mo> </mrow> <mi>max</mi> </msub> <mo>&le;</mo> <mi>&Delta;</mi> <msub> <mi>v</mi> <mi>max</mi> </msub> </mtd> </mtr> <mtr> <mtd> <mi>&lambda;</mi> <mo>&le;</mo> <mi>&Delta;</mi> <msub> <mi>a</mi> <mi>max</mi> </msub> <msub> <mi>T</mi> <mi>s</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow></math>

wherein | Δ v (k) & gtY_maxThe calculation formula of the maximum amplitude term of the speed difference control quantity sequence is as follows:

|Δv(k)|_max＝|Δv(0)|or|Δv(N-1)| (3)

λ is the variation step length of the speed difference control quantity sequence, and the calculation formula is as follows:

<math><mrow> <mi>&lambda;</mi> <mo>=</mo> <mi>&Delta;a</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mn>3</mn> <mo>[</mo> <mi>Nv</mi> <msub> <mi>T</mi> <mi>s</mi> </msub> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> <mo>-</mo> <mn>2</mn> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> <mo>]</mo> <mtext></mtext> </mrow> <mrow> <mrow> <mo>(</mo> <msup> <mi>N</mi> <mn>3</mn> </msup> <mo>-</mo> <mi>N</mi> <mo>)</mo> </mrow> <mfrac> <msub> <mi>T</mi> <mi>s</mi> </msub> <mi>W</mi> </mfrac> <mi>v</mi> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow></math>

Δv_maxand Δ a_maxSetting the maximum amplitude and the maximum change rate of the speed in advance;

when the deviation of the direction angle is larger than 5 degrees, the single-step prediction intelligent control adopts a kinematic model to calculate a single-step control quantity meeting the optimal deviation state conversion strategy, so that the deviation of two paths is quickly and stably reduced, and when the deviation of the direction angle is reduced to 5 degrees, the multi-step prediction optimal control is utilized;

(a) if the path deviation e_θ(k) And e_d(k) An opposite sign, or e_d(k) When the direction angle deviation is eliminated, the speed difference control amount is calculated as 0:

<math><mrow> <mi>&Delta;v</mi> <msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mi>p</mi> </msup> <mo>=</mo> <mo>-</mo> <mfrac> <mrow> <mi>W</mi> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> <mrow> <mn>2</mn> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow></math>

(b) if the path deviation e_θ(k) And e_d(k) Same number, or e_θ(k) When the speed difference control quantity is equal to 0, the speed difference control quantity for synchronously eliminating two deviations is calculated:

<math><mrow> <mi>&Delta;v</mi> <msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mi>P</mi> </msup> <mo>=</mo> <mo>-</mo> <mi>v</mi> <mfrac> <mrow> <mi>W</mi> <mi>tan</mi> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mi>tan</mi> <mfrac> <mrow> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> <mn>2</mn> </mfrac> </mrow> <mrow> <mn>2</mn> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow></math>

if | Δ v (k)^P|＜Δv_minWherein, Δ v_minAnd adjusting the speed difference control quantity according to the following formula for the preset speed minimum amplitude:

Δv(k)^P＝Δv(k-1)+sign(e_d(k))λ_min (7)

wherein, $\mathrm{sign}\left(x\right)=\left\{\begin{array}{cc}1& x>0\\ 0& x=0\\ -1& x<0\end{array}\right..---\left(8\right)$

λ_mina preset speed minimum change rate;

(c) if | Δ v (k)^P-Δv(k-1)|≤λ_maxWherein λ is_max＝Δa_maxT_sThen the calculation formula of the speed difference control quantity is

Δv(k)＝Δv(k)^P (9)

Otherwise, the calculation formula of the speed difference control quantity is

Δv(k)＝Δv(k-1)+sign(Δv(k)^P-Δv(k-1))λ_max (10)

If | Δ v (k)^P|＞Δv_maxThen the calculation formula of the speed difference control quantity is

Δv(k)＝sign(Δv(k)^P)Δv_max (11)

Compared with the existing motion control method of the automatic guided vehicle, the method has the following advantages: (1) the characteristics of the separable differential driving device are fully utilized, and the conventional wheel type moving mechanism with simple structure and high cost performance is adopted to realize the omnibearing movement along any direction. (2) The control principle is simple, and the free and accurate adjustment of the lower rotary table and even the movement direction of the vehicle body is realized by adopting the locking-unlocking-locking control process between the lower rotary table and the vehicle body. (3) The method has the advantages that the path adaptability is good, a high-stability free state tracking control method is adopted for the running path with complex shape change, the position and the posture of the vehicle body are accurately adjusted by adopting an all-directional tracking control method for the parking positioning point, and the vehicle can rapidly move by adopting a locked state tracking control method for the long-distance running path.

Drawings

Fig. 1 is a front view schematically showing the structure of the dividable differential drive apparatus of the present invention.

Fig. 2 is a schematic top view of an omni-directional mobile automated guided vehicle to which the apparatus of the present invention is applied.

Fig. 3 is a control system schematic of the apparatus of the present invention.

Fig. 4 is a schematic view of the connection of the split differential drive apparatus to the vehicle body.

Fig. 5 is a control schematic diagram for adjusting the moving direction of the vehicle body in all directions.

Fig. 6 is a schematic diagram illustrating the components of the path adaptive tracking control method according to the present invention.

Fig. 7 is a control schematic diagram of the free-state tracking control method.

Fig. 8 is a control diagram of the omni-directional tracking control method.

Fig. 9 is a schematic diagram of a kinematic model of a lock-state tracking control method.

FIG. 10 is a deviation state classification diagram of the lock state tracking control method.

FIG. 11 is a schematic diagram of synchronous rectification for the lock state tracking control method.

FIG. 12 is a schematic diagram of an optimal bias state transition strategy for a lock state tracking control method.

Number designation in the figures: 1. an upper turntable; 2. a thrust bearing; 3. an angle sensor; 4. a lower turntable; 5. an electromagnetic clutch; 6. a friction block; 7. a right rotary encoder; 8. a right motor brake; 9. a right servo motor; 10. a right speed reducer; 11. a right drive wheel; 12. a right drive wheel connecting key; 13. a right bearing seat; 14. a right rolling bearing; 15. a right fastening bolt; 16. a right retainer ring; 17. a left retainer ring; 18. a left fastening bolt; 19. a left rolling bearing; 20. a left bearing seat; 21. a left drive wheel connecting key; 22. a left drive wheel; 23. a left speed reducer; 24. a left servo motor; 25. a left motor brake; 26. a left rotary encoder; 27. a vehicle body; 28. a right motor driver; 29. a left motor driver; 30. a guide sensor; 31. a vehicle-mounted controller; 32. a freewheel 1; 33. a freewheel 2; 34. a freewheel 3; 35. a free wheel 4; 36. controlling the storage battery pack; 37. driving the storage battery pack; 38. a guide bolt; 39. a load bearing spring; 40. and fastening the bolt. Further, the Y-axis is the self-direction of the vehicle body 27, and the Y-axis is the self-direction of the lower dial 4.

Detailed Description

The constituent structure of the separable differential drive apparatus and the operation of the path adaptive tracking control method according to the present invention will be described in detail below with reference to the embodiments shown in the drawings.

Referring to fig. 1, the separable differential driving apparatus of the present invention is composed of an upper rotary disk 1 and a lower rotary disk 4 which are separable, wherein the upper rotary disk 1 has a central hole, and the upper end surface of the lower rotary disk 4 has a central shaft; the central hole of the upper turntable 1 and the central shaft of the lower turntable 4 are coaxially assembled through a thrust bearing 2; the central shaft of the lower rotary table 4 can be ensured to freely rotate in the central hole of the upper rotary table 1 while bearing the axial load. A cylindrical electromagnetic clutch 5 is also arranged between the central hole of the upper rotary table 1 and the central shaft of the lower rotary table 4.

Referring to fig. 1 and 2, two sets of wheel-type moving devices are symmetrically installed on the lower turntable 4 along two sides of the central shaft, the right wheel-type moving device comprises a right motor driver 28, a right motor brake 8, a right servo motor 9, a right rotary encoder 7, a right speed reducer 10 and a right driving wheel 11, and the left wheel-type moving device comprises a left motor driver 29, a left motor brake 25, a left servo motor 24, a left rotary encoder 26, a left speed reducer 23 and a left driving wheel 22;

the lower rotary table 4 is also provided with a guide sensor 30 for detecting the path deviation and a vehicle-mounted controller 31 for realizing autonomous driving;

wherein, the output ends of the right motor driver 28 and the left motor driver 29 are respectively electrically connected with the input ends of the right servo motor 9 and the left servo motor 24, the right motor brake 8 and the left motor brake 25 are respectively mechanically connected with the output shafts of the right servo motor 9 and the left servo motor 24 in a clutch mode, the rotors of the right rotary encoder 7 and the left rotary encoder 26 are respectively connected with the output shafts of the right servo motor 9 and the left servo motor 24 in a key mode, the output shafts of the right servo motor 9 and the left servo motor 24 are respectively connected with the input shafts of the right speed reducer 10 and the left speed reducer 23 in a coupling mode, the output shafts of the right speed reducer 10 and the left speed reducer 23 are respectively connected with the hubs of the right driving wheel 11 and the left driving wheel 22 in a key mode, the output shafts of the right speed reducer 10 and the left speed reducer 23 are respectively connected with the right bearing seat 13 and the left bearing seat 20 in a right rolling bearing 14 and a left rolling bearing 19 And an output shaft end surface of the left speed reducer 23. The guide sensor 30, the right rotary encoder 7 and the left rotary encoder 26 are connected with the vehicle-mounted controller 31 through a signal input circuit; the vehicle-mounted controller 31 is respectively connected with the right motor driver 28 and the left motor driver 29, the right motor brake 8 and the left motor brake 25 through signal output circuits.

Referring to fig. 2 and 3, the on-board controller 31 detects a path deviation of the lower turntable 4 from the ground guide mark line through the guide sensor 30; the motion speed and direction of the right servo motor 9 and the left servo motor 24 are independently controlled through a right motor driver 28 and a left motor driver 29 respectively, and the right servo motor 9 and the left servo motor 24 are immediately braked through a right motor brake 8 and a left motor brake 25; the right speed reducer 10 and the left speed reducer 23 are driven by the right servo motor 9 and the left servo motor 24, the rotating speed and the torque are transmitted to the right driving wheel 11 and the left driving wheel 22, and the moving speed and the moving direction of each driving wheel can be independently and accurately controlled; and feeds back the speed and displacement information of each driving wheel to the on-board controller 31 through the right rotary encoder 7 and the left rotary encoder 26. When the two driving wheels have the same speed and the same direction, the lower turntable 4 moves along a linear track; when the two driving wheels have different speeds and the same direction, the lower turntable 4 moves along a curved track; when the two driving wheels have equal speed and opposite directions, the lower turntable 4 rotates around the central shaft in situ.

Referring to fig. 1 and 2, the upper rotary disk 1 is mounted with an angle sensor 3 that detects a rotation angle between it and the lower rotary disk 4. The shell of the sensor is fixed on the upper end face of the upper rotary table 1, the rotor of the sensor is connected with the central shaft of the lower rotary table 4 through a key and is connected with the vehicle-mounted controller 31 on the lower rotary table 4 through a signal input circuit, the rotating angle between the lower rotary table 4 and the upper rotary table 1 is fed back, and the moving direction angle of the lower rotary table 4 can be calculated according to the rotating angle.

Referring to fig. 1 and 2, the casing of the electromagnetic clutch 5 is fixed in the central hole of the upper turntable 1, and whether the electromagnetic coil is electrified or not is controlled by the driving circuit of the vehicle-mounted controller 31, and the clutch type mechanical connection is performed between the friction blocks 6 which are evenly distributed in the circumferential direction and the central shaft of the lower turntable 4. When the electromagnetic coil of the electromagnetic clutch 5 is electrified, the friction block 6 is sucked back, the friction block has no pressing effect on the central shaft of the lower rotary disk 4, and the central shaft of the lower rotary disk 4 can freely rotate in the central hole of the upper rotary disk 1, so that the rotating angle between the lower rotary disk 4 and the upper rotary disk 1 is adjusted. When the electromagnetic coil of the electromagnetic clutch 5 is powered off, the pressure spring pushes the friction block 6 to press the central shaft of the lower rotary disk 4, and the lower rotary disk 4 and the upper rotary disk 1 do not rotate relatively.

Referring to fig. 2 and 4, the separable differential drive unit is mounted in the lower center of the vehicle body 27. According to the bearing capacity of the automatic guided vehicle and the smoothness of the running road surface, the upper turntable 1 and the vehicle body 27 can be rigidly and fixedly connected by a fastening bolt 40, and can also be flexibly suspended and connected by a guide bolt 38 and a bearing spring 39. The two connections differ only in whether a vertical displacement between the upper turntable 1 and the vehicle body 27 is possible, but no relative movement in the horizontal direction is possible, so that a free rotation of the lower turntable 4 relative to the upper turntable 1 is a free rotation of the lower turntable 4 relative to the vehicle body 27. 2 free wheels with supporting function are respectively arranged at the front part and the rear part below the vehicle body 27, the moving speed and the moving direction of the free wheels depend on the moving state of the vehicle body 27, and the steering of the automatic guided vehicle is realized by matching with the driving wheel of the lower turntable 4.

A control battery pack 36 for supplying power to the angle sensor 3, the right rotary encoder 7, the left rotary encoder 26, the guide sensor 30 and the vehicle-mounted controller 31 is also mounted on the vehicle body 27; a drive battery pack 37 for supplying power to the electromagnetic clutch 5, the right motor brake 8, the left motor brake 25, the right motor driver 28, and the left motor driver 29 is also mounted on the vehicle body 27. Because the battery pack with large mass and the load are both arranged on the vehicle body 27, the inertia of the lower turntable 4 is small, and the steering and straight-going motion can be flexibly completed through the differential control of the two driving wheels.

Referring to fig. 5, the control process for omni-directionally adjusting the moving direction of the vehicle body is as follows:

in fig. 5, (a), the vehicle body 27 is first brought to a standstill, the on-board controller 31 controls the energization of the electromagnetic coil of the electromagnetic clutch 5 through its drive circuit, and the friction block 6 is sucked back, which has no pressing effect on the center shaft of the lower dial 4. The vehicle-mounted controller 31 controls the right servo motor 9 through the right motor driver 28, and drives the right driving wheel 11 to rotate reversely through the right speed reducer 10; the left servo motor 24 is controlled by a left motor driver 29, and a left driving wheel 22 is driven to rotate in the positive direction by a left speed reducer 23; and ensures that the rotating speeds of the right driving wheel 11 and the left driving wheel 22 are the same, and the central shaft of the lower rotary table 4 freely rotates in the central hole of the upper rotary table 1.

Because the mass of the vehicle body 27 is far greater than that of the lower turntable 4, and the friction force exerted on the central shaft of the lower turntable 4 to rotate in the central hole of the upper turntable 1 is very small, the lower turntable 4 rotates in place around the central shaft while the posture (i.e., the Y-axis direction) of the vehicle body 27 is kept unchanged, and the movement direction (i.e., the Y-axis direction) of the lower turntable 4 is freely and accurately adjusted. In the process, the on-board controller 31 detects the rotation angle between the lower turntable 4 and the vehicle body 27, i.e. the included angle between the Y-axis and the Y-axis, in real time through the angle sensor 3.

In fig. 5.(b), when the angle reaches a predetermined movement direction angle (in the embodiment, the angle between the Y-axis and the Y-axis is 90 °), the on-board controller 31 controls the right and left servo motors 9 and 24 to stop rotating through the right and left motor drivers 28 and 29, and immediately brakes the right and left servo motors 9 and 24 through the right and left motor brakes 8 and 25.

Then, the vehicle-mounted controller 31 controls the electromagnetic coil of the electromagnetic clutch 5 to be powered off through a driving circuit thereof, the pressure spring pushes the friction block 6 to press the central shaft of the lower rotary disk 4, the lower rotary disk 4 and the vehicle body 27 do not rotate relatively, and the included angle between the Y axis and the Y axis is locked to be a preset movement direction angle.

Referring to fig. 6, the invention adopts a self-adaptive tracking control method for the separable differential drive automatic guided vehicle aiming at the running paths with different shapes: for a curve path with complicated shape change, the locking between the lower turntable 4 and the vehicle body 27 is released, and a high-stability free-state tracking control method is adopted; for a parking positioning point on a straight line path, the position and the posture of the vehicle body are accurately adjusted by an omnibearing tracking control method by utilizing the locking-unlocking-locking control process between the lower turntable 4 and the vehicle body 27; for long distance road sections on the straight line path, the lower rotary table 4 and the vehicle body 27 are locked, and the vehicle is quickly moved by adopting a locking state tracking control method.

Referring to fig. 7, the control process of the free state tracking control method of the present invention is as follows: when the automatic guided vehicle enters a curve path with complicated shape change, the vehicle-mounted controller 31 controls the electromagnetic coil of the electromagnetic clutch 5 to be electrified through the driving circuit thereof, the friction block 6 is sucked back, the friction block has no pressing effect on the central shaft of the lower turntable 4, and the locking between the lower turntable 4 and the vehicle body 27 is released.

On one hand, only a guide sensor 30 with light weight, a vehicle-mounted controller 31 and two sets of wheel-type moving devices are arranged on the lower turntable 4, and the guide sensor 30 can be used for detecting the path deviation of the ground guide marking in real time and sending the path deviation to the vehicle-mounted controller 31; the vehicle-mounted controller 31 outputs the speed difference control quantity of the two driving wheels through efficient deviation correction calculation, and then accurately controls the actual speed of the right driving wheel 11 and the actual speed of the left driving wheel 22 through the right servo motor 9 and the left servo motor 24 respectively, so that the lower turntable 4 with small inertia can adjust the position and the posture of the lower turntable in time according to the shape change of a curve path. In the path tracking process shown in fig. 7, the center of the lower dial 4 is always located on the curved path, and its own direction (y-axis) is always directed to the tangential direction of the curved path. Therefore, the control method remarkably improves the rapidity and the accuracy of the lower turntable 4 in the path tracking process, and completely avoids the problem of tracking failure caused by the fact that the ground guide marking line exceeds the effective detection range of the guide sensor 30.

On the other hand, since the battery pack and the load having a heavy weight are mounted on the vehicle body 27, it is difficult for the vehicle body 27 having a large inertia to adjust its position and posture in time in accordance with the change in the shape of the curved path. Therefore, the vehicle body 27 does not directly follow the shape change of the curved path, but rotates around the central axis of the lower turntable 4 while moving along with the moving direction of the lower turntable 4 under the driving of the lower turntable 4. During the path tracking, the rate of change of the attitude angle of the vehicle body 27 is slower than that of the lower turntable 4, and as in the position of fig. 7.(a), the own direction (Y-axis) of the lower turntable 4 starts to deflect in the tangential direction of the curved path, while the own direction (Y-axis) of the vehicle body 27 is still along the original straight path direction. Also, the amplitude of the change in the attitude angle of the vehicle body 27 is smaller than that of the lower turntable 4, as shown by the broken line and the solid line in fig. 7. Therefore, the influence of the rapidly-changed operation pose state of the lower rotary table 4 on the vehicle body 27 is limited, and the control method can ensure the stability of the vehicle body 27 in the operation on a complex curve path.

Referring to fig. 5 and 8, the omni-directional tracking control method of the present invention realizes the movement of the automated guided vehicle in any direction by using the locking-unlocking-locking control process between the lower turntable and the vehicle body. The control process of the omni-directional tracking control method will be described by taking the direct elimination of the lateral position deviation of the automated guided vehicle in fig. 8 as an example.

In fig. 8.(a), the angular deviation between the automated guided vehicle and the travel path is 0, and the lateral position deviation is e_dThe following is to directly eliminate e while keeping the direction (Y-axis) of the vehicle body 27 itself unchanged_d。

In fig. 8 (b), the automated guided vehicle is stopped, and the lock between the lower turntable 4 and the vehicle body 27 is released by the electromagnetic clutch 5 in the separable differential drive device. The guide sensor 30 detects a path deviation between the vehicle body 27 and the ground guide mark line and sends it to the on-vehicle controller 31; the vehicle-mounted controller 31 calculates the motion direction angle of the automatic guided vehicle according to the motion direction angle, and further calculates that the lower turntable 4 needs to rotate 90 degrees clockwise relative to the vehicle body 27; the vehicle-mounted controller 31 controls the right driving wheel 11 to rotate reversely through the right servo motor 9, controls the left driving wheel 22 to rotate forwardly through the left servo motor 24, and keeps the speeds of the two wheels the same; the lower turntable 4 rotates clockwise around its central axis, and the onboard controller 31 detects the rotation angle between the lower turntable 4 and the vehicle body 27 in real time through the angle sensor 3. When the rotation angle reaches 90 °, the on-vehicle controller 31 stops the right servo motor 9 and the left servo motor 24, and immediately brakes by the right motor brake 8 and the left motor brake 25, and the lower dial 4 stops rotating, and its own direction (y-axis) is adjusted to be perpendicular to the vehicle body side direction of the running path.

In fig. 8.(c), the lower turntable 4 and the vehicle body 27 are locked by the electromagnetic clutch 5 in the separable differential drive device, and the angle between the direction of the lower turntable 4 itself (Y-axis) and the direction of the vehicle body 27 itself (Y-axis) is maintained at 90 °. The vehicle-mounted controller 31 precisely controls the right driving wheel 11 and the left driving wheel 22 to rotate forwards at the same speed through the right servo motor 9 and the left servo motor 24, and the automatic guided vehicle guides the marked line to move along the y axis to the ground surface while keeping the posture of the vehicle body 27 unchanged. The guide sensor 30 detects the lateral position deviation e of the automated guided vehicle in real time_dWhen e is_dWhen the zero time is eliminated, the vehicle-mounted controller 31 stops the right servo motor 9 and the left servo motor 24, and immediately brakes the vehicle by the right motor brake 8 and the left motor brake 25, so that the vehicle is automatically guided to stop moving.

In fig. 8.(d), the lock between the lower turntable 4 and the vehicle body 27 is released by the electromagnetic clutch 5 in the separable differential drive device. The vehicle-mounted controller 31 calculates that the lower turntable 4 needs to rotate 90 degrees counterclockwise relative to the vehicle body 27 according to the existing posture of the vehicle body 27; the vehicle-mounted controller 31 controls the right driving wheel 11 to rotate in the forward direction through the right servo motor 9, controls the left driving wheel 22 to rotate in the reverse direction through the left servo motor 24, and keeps the speeds of the two wheels the same; the lower turntable 4 rotates counterclockwise around its center axis, and the onboard controller 31 detects the rotation angle between the lower turntable 4 and the vehicle body 27 in real time through the angle sensor 3. When the rotation angle reaches 90 °, the on-vehicle controller 31 stops the right servomotor 9 and the left servomotor 24, and immediately brakes by the right motor brake 8 and the left motor brake 25, and the lower dial 4 stops rotating, and its own direction (Y axis) is restored to coincide with the own direction (Y axis) of the vehicle body 27. Finally, the lower rotary table 4 and the vehicle body 27 are locked through an electromagnetic clutch 5 in the separable differential driving device.

Referring to FIG. 9, the present invention is describedThe locking state tracking control method locks the lower turntable 4 and the vehicle body 27 through an electromagnetic clutch 5 in the separable differential driving device, wherein Sigma XOY is a fixed coordinate system, Sigma XOY is a vehicle-mounted coordinate system of the vehicle body 27, and the abscissa of the intersection point of the guide marking line and the x axis is lateral position deviation e_dThe included angle between the tangent direction of the guide marking line and the y axis is the direction angle deviation e_θWhen the tangential direction turns counterclockwise to the y-axis e_θ< 0, e when steering clockwise the y-axis_θIs greater than 0. The linear velocities of the left and right drive wheels 22 and 11, respectively, are v_lAnd v_rThe translational linear velocity at the center of the vehicle body 27 is v, and the rotational angular velocity is ω.

When the guide sensor 30 detects the path deviation, the onboard controller 31 generates a speed difference control amount Δ v between the right driving wheel 11 and the left driving wheel 22 through motor servo control, so that the vehicle body 27 moves along an arc track with an instantaneous center C to eliminate the path deviation and keep the central linear speed v of the vehicle body 27 constant, that is, the central linear speed v of the vehicle body 27 is constant

<math><mrow> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msub> <mi>v</mi> <mn>1</mn> </msub> <mo>=</mo> <mi>v</mi> <mo>+</mo> <mi>&Delta;v</mi> </mtd> </mtr> <mtr> <mtd> <msub> <mi>v</mi> <mi>r</mi> </msub> <mo>=</mo> <mi>v</mi> <mo>-</mo> <mi>&Delta;v</mi> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow></math>

Assuming that the distance between the right drive wheel 11 and the left drive wheel 22 is W, the angular velocity of the vehicle body 27 rotating along the instant center C is:

<math><mrow> <mi>&omega;</mi> <mo>=</mo> <mfrac> <mrow> <mo>(</mo> <msub> <mi>v</mi> <mn>1</mn> </msub> <mo>-</mo> <msub> <mi>v</mi> <mi>r</mi> </msub> <mo>)</mo> </mrow> <mi>W</mi> </mfrac> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>&Delta;v</mi> </mrow> <mi>W</mi> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow></math>

let the control period of the onboard controller 31 be T_sLet e be the angular deviation of the direction of the current state k_θ(k) The following direction angle deviation of the next state k +1 is:

<math><mrow> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>+</mo> <mfrac> <mrow> <mn>2</mn> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> <mi>W</mi> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow></math>

the lateral distance deviation for the next state k +1 is:

<math><mrow> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>-</mo> <mi>v</mi> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> <mo>-</mo> <mfrac> <mrow> <mi>v&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msubsup> <mi>T</mi> <mi>s</mi> <mn>2</mn> </msubsup> </mrow> <mi>W</mi> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow></math>

the kinematic model of the automated guided vehicle is as follows:

<math><mrow> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>+</mo> <mfrac> <mrow> <mn>2</mn> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> <mi>W</mi> </mfrac> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>-</mo> <mi>v</mi> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> <mo>-</mo> <mi>v</mi> <mfrac> <msubsup> <mi>T</mi> <mi>s</mi> <mn>2</mn> </msubsup> <mi>W</mi> </mfrac> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow></math>

considering the limited performance capability of the servo motor and the motor driver, the amplitude and the variation step of the speed difference control quantity Δ v (k) must satisfy the following conditions:

<math><mrow> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mo>|</mo> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>|</mo> <mo>&le;</mo> <mi>&Delta;</mi> <msub> <mi>v</mi> <mi>max</mi> </msub> </mtd> </mtr> <mtr> <mtd> <mi>&lambda;</mi> <mo>=</mo> <mo>|</mo> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>-</mo> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>|</mo> <mo>&le;</mo> <mi>&Delta;</mi> <msub> <mi>a</mi> <mi>max</mi> </msub> <msub> <mi>T</mi> <mi>s</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow></math>

wherein, Δ v_maxAnd Δ a_maxThe maximum amplitude and the maximum change rate of the speed are preset.

Under the constraint of the condition (6), the path deviation of the current state may not be completely eliminated in one control cycle, and from the perspective of the overall optimization of multiple control cycles, an N-step optimal control sequence Δ v (k) is designed with the objective of optimizing the coordination of eliminating two path deviations, where (k is 0, 1.. N-1), and the two path deviations are eliminated to zero at the same time, that is, the control objective is met:

<math><mrow> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>N</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mi>N</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>7</mn> <mo>)</mo> </mrow> </mrow></math>

the fastest deviation elimination process which can be realized by the motor driving system can be achieved by minimizing the control step number N under the constraint of the condition (6). On the basis, quadratic integral of speed difference control quantity is used as an objective function for describing deviation rectification coordination, namely

<math><mrow> <mi>J</mi> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <mi>&Delta;</mi> <msup> <mi>v</mi> <mn>2</mn> </msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>8</mn> <mo>)</mo> </mrow> </mrow></math>

When the deviation of the direction angle is not more than 5 degrees, the locking state tracking control method adopts multi-step prediction optimal control, realizes a deviation elimination process with optimal coordination and rapidity achieved by the motor driving system capacity for a system with a state equation (5) under the constraint of a condition (6) by minimizing an objective function (8) and the control step number N, finally meets a control target (8), and simultaneously eliminates the deviation of two paths to zero and maintains a non-deviation tracking state.

According to Lagrange undetermined sequence method, introducing undetermined sequence to a state equation (5):

{λ(k+1)}＝{[λ₁(k+1)λ₂(k+1)]^T} (9)

the Hamilton function is:

<math><mrow> <mi>H</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mi>&Delta;</mi> <msup> <mi>v</mi> <mn>2</mn> </msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>+</mo> <mi>&lambda;</mi> <msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>T</mi> </msup> <mo>{</mo> <mfenced open='' close=''> <mtable> </mtable> </mfenced> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>-</mo> <mi>v</mi> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>+</mo> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <mfrac> <mrow> <mn>2</mn> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> <mi>W</mi> </mfrac> </mtd> </mtr> <mtr> <mtd> <mo>-</mo> <mfrac> <mrow> <mi>v</mi> <msubsup> <mi>T</mi> <mi>s</mi> <mn>2</mn> </msubsup> </mrow> <mi>W</mi> </mfrac> </mtd> </mtr> </mtable> </mfenced> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>}</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>10</mn> <mo>)</mo> </mrow> </mrow></math>

the speed difference control quantity sequence delta v (k) enabling the objective function (8) to obtain a minimum value satisfies the following condition:

<math><mrow> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>&lambda;</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mrow> <mo>&PartialD;</mo> <mi>H</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> <mrow> <mo>&PartialD;</mo> <mi>X</mi> <mrow> <mo>(</mo> <mi>K</mi> <mo>)</mo> </mrow> </mrow> </mfrac> </mtd> </mtr> <mtr> <mtd> <mfrac> <mrow> <mo>&PartialD;</mo> <mi>H</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> <mrow> <mo>&PartialD;</mo> <mi>u</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>=</mo> <mn>0</mn> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>11</mn> <mo>)</mo> </mrow> </mrow></math>

the sequence of speed difference control amounts obtainable from the condition (11) is:

<math><mrow> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <mo>-</mo> <mfrac> <mrow> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> </mrow> <mrow> <mn>2</mn> <mi>N</mi> <mfrac> <msub> <mi>T</mi> <mi>s</mi> </msub> <mi>W</mi> </mfrac> </mrow> </mfrac> <mo>+</mo> <mn>3</mn> <mrow> <mo>(</mo> <mi>k</mi> <mo>-</mo> <mfrac> <mrow> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow> <mn>2</mn> </mfrac> <mo>)</mo> </mrow> <mo>[</mo> <mfrac> <mrow> <mi>Nv</mi> <msub> <mi>T</mi> <mi>s</mi> </msub> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> <mo>-</mo> <mn>2</mn> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> </mrow> <mrow> <mrow> <mo>(</mo> <msup> <mi>N</mi> <mn>3</mn> </msup> <mo>-</mo> <mi>N</mi> <mo>)</mo> </mrow> <mfrac> <msub> <mi>T</mi> <mi>s</mi> </msub> <mi>W</mi> </mfrac> <mi>v</mi> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> </mfrac> <mo>]</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>12</mn> <mo>)</mo> </mrow> </mrow></math>

wherein, the total step number N of the control quantity sequence is more than or equal to 2, and the current control step number k is 0, 1, 2.

In the speed difference control quantity sequence, the calculation formula of the maximum amplitude term is as follows:

|Δv(k)|_max＝|Δv(0)|or|Δv(N-1)| (13)

the change step of the speed difference control quantity sequence is as follows:

<math><mrow> <mi>&lambda;</mi> <mo>=</mo> <mi>&Delta;a</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msub> <mi>T</mi> <mi>s</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mn>3</mn> <mo>[</mo> <mi>Nv</mi> <msub> <mi>T</mi> <mi>s</mi> </msub> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> <mo>-</mo> <mn>2</mn> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mn>0</mn> <mo>)</mo> </mrow> <mo>]</mo> <mtext></mtext> </mrow> <mrow> <mrow> <mo>(</mo> <msup> <mi>N</mi> <mn>3</mn> </msup> <mo>-</mo> <mi>N</mi> <mo>)</mo> </mrow> <mfrac> <msub> <mi>T</mi> <mi>s</mi> </msub> <mi>W</mi> </mfrac> <mi>v</mi> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>14</mn> <mo>)</mo> </mrow> </mrow></math>

to ensure that all of the velocity difference control amounts Δ v (k) satisfy the condition (6), it is only necessary to satisfy

<math><mrow> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msub> <mrow> <mo>|</mo> <mi>&Delta;v</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>|</mo> </mrow> <mi>max</mi> </msub> <mo>&le;</mo> <mi>&Delta;</mi> <msub> <mi>v</mi> <mi>max</mi> </msub> </mtd> </mtr> <mtr> <mtd> <mi>&lambda;</mi> <mo>&le;</mo> <mi>&Delta;</mi> <msub> <mi>a</mi> <mi>max</mi> </msub> <msub> <mi>T</mi> <mi>s</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>15</mn> <mo>)</mo> </mrow> </mrow></math>

From the condition (15), the total step number N of the controlled variable sequence of the multi-step predictive optimal control can be calculated.

Referring to fig. 10, the locking state tracking control method of the present invention is divided into four deviation states according to the relationship between two path deviations, and studies the conversion process between the deviation states for the large deviation condition that the direction angle deviation is greater than 5 °, rapidly and smoothly reduces the two path deviations through single step prediction intelligent control, and then utilizes the multi-step prediction optimal control when the direction angle deviation is reduced to 5 °.

Referring to fig. 11, the single-step prediction intelligent control of the invention ensures that the moving direction of the automatic guided vehicle is tangentially transited to the guide marked line from the y axis of the vehicle-mounted coordinate system along the arc oB taking a point C as the center of a circle and taking an R as the radius under the same sign deviation state, the deviation of two paths can be synchronously eliminated to zero, and the moving radius is

<math><mrow> <mo>|</mo> <mi>R</mi> <mo>|</mo> <mo>=</mo> <mi>oC</mi> <mo>=</mo> <mfrac> <mi>oA</mi> <mrow> <mi>tan</mi> <mo>&angle;</mo> <mi>oCA</mi> </mrow> </mfrac> <mo>=</mo> <mfrac> <mrow> <mo>|</mo> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>|</mo> </mrow> <mrow> <mo>|</mo> <mi>tan</mi> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mi>tan</mi> <mfrac> <mrow> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> <mn>2</mn> </mfrac> <mo>|</mo> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>16</mn> <mo>)</mo> </mrow> </mrow></math>

When the speed difference control amount is not zero, the following relationship exists between the radius of the circular motion and the angular velocity:

<math><mrow> <mi>R</mi> <mo>=</mo> <mfrac> <mi>v</mi> <mi>&omega;</mi> </mfrac> <mo>=</mo> <mfrac> <mi>vW</mi> <mrow> <mn>2</mn> <mi>&Delta;v</mi> </mrow> </mfrac> <mo>,</mo> <mi>&Delta;v</mi> <mo>&NotEqual;</mo> <mn>0</mn> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>17</mn> <mo>)</mo> </mrow> </mrow></math>

the speed difference control amount for synchronously eliminating two deviations from the equations (16) and (17) is:

<math><mrow> <mi>&Delta;v</mi> <msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mi>P</mi> </msup> <mo>=</mo> <mo>-</mo> <mi>v</mi> <mfrac> <mrow> <mi>W</mi> <mi>tan</mi> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mi>tan</mi> <mfrac> <mrow> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> <mn>2</mn> </mfrac> </mrow> <mrow> <mn>2</mn> <msub> <mi>e</mi> <mi>d</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>18</mn> <mo>)</mo> </mrow> </mrow></math>

in view of the requirement for rapidity of the offset cancellation process, the speed difference control amount calculated by equation (18) needs to satisfy:

|Δv(k)^P|≥Δv_min (19)

wherein, Δ v_minIs a preset minimum amplitude of velocity.

If the condition (19) is met, defining the same-sign deviation state as a same-sign deviation I state, and directly adopting the synchronous speed difference control quantity calculated by the formula (18); otherwise, defining as the state of same sign deviation II, and for converting to the state of same sign deviation I, the ratio of the direction angle deviation to the lateral position deviation needs to be increased, and the speed difference control quantity is adjusted towards the direction of increasing the direction angle deviation, that is to say

Δv(k)^P＝Δv(k-1)+sign(e_d(k))λ_min (20)

Wherein, $\mathrm{sign}\left(x\right)=\left\{\begin{array}{cc}1& x>0\\ 0& x=0\\ -1& x<0\end{array}\right..---\left(21\right)$

λ_minthe preset minimum rate of change for the speed.

For the zero angle deviation state, the speed difference control amount calculated by equation (18) is zero, and this deviation state can be regarded as a special case of the state of the same sign deviation II.

As can be seen from equation (5), the direction angle deviation will generate new lateral distance deviation continuously for the different sign deviation state and the zero distance deviation state, and therefore, the direction angle deviation needs to be eliminated as soon as possible. From equation (5), the speed difference control amount for eliminating the direction angle deviation to zero is:

<math><mrow> <mi>&Delta;v</mi> <msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mi>p</mi> </msup> <mo>=</mo> <mo>-</mo> <mfrac> <mrow> <mi>W</mi> <msub> <mi>e</mi> <mi>&theta;</mi> </msub> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </mrow> <mrow> <mn>2</mn> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>22</mn> <mo>)</mo> </mrow> </mrow></math>

in order to satisfy the condition (6) in terms of the amplitude and the step length of change of the speed difference control amount Deltav (k), Deltav (k) calculated by the equations (18), (20) and (22) is determined^PWhether the following conditions are satisfied:

if | Δ v (k)^P-Δv(k-1)|≤λ_maxWherein λ is_max＝Δa_maxT_sThen the calculation formula of the speed difference control quantity is

Δv(k)＝Δv(k)^P (23)

Otherwise, the calculation formula of the speed difference control quantity is

Δv(k)＝Δv(k-1)+sign(Δv(k)^P-Δv(k-1))λ_max (24)

If | Δ v (k)^P|＞Δv_maxThen the calculation formula of the speed difference control quantity is

Δv(k)＝sign(Δv(k)^P)Δv_max (25)

Referring to fig. 12, the single-step prediction intelligent control of the invention is to reduce the deviation of two paths rapidly and smoothly, and an optimal deviation state conversion strategy is designed according to the conversion process between deviation states. For the different sign deviation state and the zero distance deviation state, the direction angle deviation generates new lateral distance deviation continuously, the formula (22) is adopted to eliminate the direction angle deviation to zero as soon as possible, and the direction angle deviation is converted into a zero angle deviation state and a same sign deviation II state. At this time, since the synchronous speed difference control amount calculated by the equation (18) is small and does not satisfy the requirement for rapidity in the offset canceling process, the speed difference control amount is adjusted in a direction of increasing the angular deviation by the equation (20) to shift to the state of the same sign offset I. At the moment, the speed difference control quantity for synchronously eliminating the deviation of the two paths can be calculated according to the formula (18), and if the control quantity meets the constraint of the condition (15), the tracking state is in a non-deviation tracking state; otherwise, the state is converted into an opposite sign deviation state, and the cycle process of the deviation state conversion is entered again.

Claims (3)

1. A separable differential driving device of a wheeled electric vehicle is characterized by comprising an upper turntable (1) and a lower turntable (4), wherein the upper turntable (1) is provided with a central hole, and the upper end surface of the lower turntable (4) is provided with a central shaft; the central hole of the upper turntable (1) and the central shaft of the lower turntable (4) are coaxially assembled through a thrust bearing (2); a cylindrical electromagnetic clutch (5) is also arranged between the central hole of the upper turntable (1) and the central shaft of the lower turntable (4);

two sets of wheel type moving devices are symmetrically installed on the lower rotary table (4) along two sides of a central shaft, the right wheel type moving device comprises a right motor driver (28), a right motor brake (8), a right servo motor (9), a right rotary encoder (7), a right speed reducer (10) and a right driving wheel (11), and the left wheel type moving device comprises a left motor driver (29), a left motor brake (25), a left servo motor (24), a left rotary encoder (26), a left speed reducer (23) and a left driving wheel (22);

the lower turntable (4) is also provided with a guide sensor (30) for detecting the path deviation and a vehicle-mounted controller (31) for realizing autonomous driving;

the guide sensor (30), the right rotary encoder (7) and the left rotary encoder (26) are connected with a vehicle-mounted controller (31) through a signal input circuit; the vehicle-mounted controller (31) is respectively connected with the right motor driver (28), the left motor driver (29), the right motor brake (8) and the left motor brake (25) through a signal output circuit;

the upper turntable (1) is provided with an angle sensor (3) for detecting the rotating angle between the upper turntable and the lower turntable, the shell of the angle sensor is fixed on the upper end surface of the upper turntable (1), and the rotor of the angle sensor is mechanically connected with the central shaft of the lower turntable (4) and is connected with an on-board controller (31) on the lower turntable (4) through a signal input circuit.

2. The separable differential drive apparatus according to claim 1, wherein the housing of the electromagnetic clutch (5) is fixed to the central hole of the upper rotary disk (1), and whether the electromagnetic coil is energized or not is controlled by the driving circuit of the vehicle controller (31), and the clutch type mechanical connection is performed between the friction blocks (6) uniformly distributed in the circumferential direction and the central shaft of the lower rotary disk (4).

3. The omni-directional mobile automated guided vehicle using the separable differential drive according to claim 1, characterized in that:

the separable differential driving device is arranged in the center below the vehicle body (27), the upper turntable (1) and the vehicle body (27) are in rigid fixed connection or flexible suspension connection, and the two devices do not move relatively in the horizontal direction;

at least 2 free wheels are arranged around the lower part of the vehicle body (27), and the moving speed and the moving direction of the free wheels depend on the moving state of the vehicle body (27);

a control battery pack (36) for supplying power to the angle sensor (3), the right rotary encoder (7), the left rotary encoder (26), the guide sensor (30) and the vehicle-mounted controller (31) is also arranged on the vehicle body (27);

and a driving battery pack (37) for supplying power to the electromagnetic clutch (5), the right motor brake (8), the left motor brake (25), the right motor driver (28) and the left motor driver (29) is also arranged on the vehicle body (27).

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