Trolley control method for eliminating downhill shaking of wall-climbing trolley

Abstract

The invention discloses a trolley control method for eliminating downhill shaking of a wall-climbing trolley, and relates to the technical field of nondestructive inspection equipment, in particular to the trolley control method for eliminating downhill shaking of the wall-climbing trolley. According to the technical scheme, wheels on the two sides of the wall-climbing trolley are driven by adopting different driving motors, when the trolley is in a downhill state, the maximum torque of one side of the driving motors on the two sides is adjusted to be small, and the rotating speed is adjusted to be large, so that when the trolley is in the downhill state, the wall-climbing trolley is driven by the driving motors on the two sides. The driving motors on the two sides apply acting force in different directions to the trolley, and the moving state of the trolley is judged by detecting the output torque of the driving motors through drivers of the driving motors. The method has the beneficial effects that the situation that the meshing state between the driving motor and the wheels is unstable when the trolley goes downhill can be effectively avoided, the stability of the trolley in the downhill process is improved, a sensor does not need to be specially arranged for detecting the moving state of the trolley, and the related cost and the control difficulty of the trolley are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of non-destructive testing equipment, and particularly relates to a car control method for eliminating shaking of a wall-climbing car when the car is going downhill. BACKGROUND

[0002] In non-destructive testing of large equipment, a car with an ultrasonic testing instrument is used to move along the surface of the equipment for testing. In order to effectively test each position on the surface of the equipment, the car needs to have a wall-climbing function, that is, the car can tightly adhere to the surface of the equipment even on steep or downwardly inclined surfaces of the equipment. At present, the car is mostly tightly adhered to the surface of the equipment by means of vacuum adsorption or magnetic adsorption. However, when the wall-climbing car is in a downhill state on the surface of the equipment, the component of the gravity of the car along the slope downward is opposite to the friction force of the surface of the equipment on the car. When the two forces are equal, the engagement state of the driving motor for driving the car to move and the wheels of the car is unstable. That is, when the driving motor provides a force along the slope downward to the wheels, the car accelerates downward, the rotation speed of the driving motor is less than the rotation speed of the wheels, and thus the driving motor provides a force along the slope upward to the wheels, so that the car enters a deceleration state. When the speed of the car is reduced to a certain degree, the rotation speed of the wheels is inconsistent with the rotation speed of the driving motor, so that the car reenters an acceleration state, and thus the car shakes when going downhill. SUMMARY

[0003] The present application aims to provide a car control method for eliminating shaking of a wall-climbing car when the car is going downhill, and particularly to provide a car control method for eliminating shaking of a wall-climbing car when the car is going downhill at low cost and effectively.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solution: a car control method for eliminating shaking of a wall-climbing car when the car is going downhill, the left wheels and the right wheels of the car are driven by different driving motors, the left motor drives the left wheels, and the right motor drives the right wheels; when the car is in a downhill state, the maximum torque of one of the left motor and the right motor is limited to aT, wherein a<1, T is the maximum torque of the left motor and the right motor when the car is normally running, the rotation speed is set to bV, wherein b>1, V is the rotation speed of the driving motor corresponding to the current speed of the car; the other driving motor or group of driving motors is not changed, and the maximum torque is kept as T and the rotation speed is kept as V; wherein the driving motor with the maximum torque aT outputs torque in the same direction as the rotation direction of the driving motor; the driving motor with the maximum torque T outputs torque in the opposite direction to the rotation direction of the driving motor; in this way, the shaking of the car during the downhill process is eliminated, and stable driving is achieved.

[0005] Preferably, the car detects whether the car is in a downhill state by the following method:

[0006] (1) At the beginning of detection, the trolley is first controlled to brake; then the maximum torque of one of the left motor and the right motor is set to aT, and the rotating speed is set to bV, aT and bV are consistent with aT and bV in claim 1, and the maximum torque of the other motor is set to T, and the rotating speed is set to V;

[0007] (2) After the brake is released, the trolley is controlled to move in the original direction, and the torque of the left motor and the right motor is detected by the driver of the left motor and the right motor,

[0008] (3) When the torque of the motor with the maximum torque set to T and the rotating speed set to V is not more than a set value cT, wherein c<1, it is considered that the trolley is in a downhill state requiring elimination of shaking, and the set parameters of the left motor and the right motor are kept unchanged.

[0009] Preferably, when detecting whether the trolley is in a downhill state, if the torque of the motor with the maximum torque set to T and the rotating speed set to V is greater than a set value cT, it is considered that the trolley is in an overload uphill state, and the maximum torque of the motor with the maximum torque set to aT and the rotating speed set to bV is set to T, and the rotating speed is set to V.

[0010] Preferably, the value of a satisfies the following conditions: (1) F aT > f 静 -G, wherein F aT is the driving force corresponding to aT, f 静 is the static friction force between the bearing and the gear when at rest, and G is the component force of gravity along the slope downward; and (2) F aT < f 动1 -G, wherein f 动1 is the longitudinal component force of the dynamic friction between the bearing and the gear when in motion; and the value of a can only drive the gear to engage without moving the trolley.

[0011] Preferably, the value of b is b>1, so as to shorten the time for the gear to start rotating to engage.

[0012] Preferably, in the downhill state, the gear of one side of the trolley is in a lower engagement state with the maximum torque aT and the rotating speed bV, and the gear of the other side of the trolley is in an upper engagement state with the maximum torque T and the rotating speed V, and the engagement states of the gears on both sides remain stable.

[0013] Preferably, after the control method of claim 1 is executed, the parameter setting is maintained for a duration t, wherein t>d / ((b-1)V), d is the maximum gap of the magnetic wheel, and V is the minimum speed of the trolley, and then the motor originally set to aT and bV is restored to the maximum torque T and the rotating speed V, so that the parameters of the motors on both sides are consistent.

[0014] The application has the beneficial effect that: by using different driving motors to drive the wheels on both sides of the wall climbing trolley, when the trolley is in a downhill state, the maximum torque of one side of the two driving motors is reduced, and the rotational speed is increased, so that the driving motors on both sides of the trolley exert different forces on the trolley when the trolley is downhill, thereby effectively avoiding the unstable engagement state between the driving motor and the wheel when the trolley is downhill, and improving the stability of the trolley during the downhill process. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows.

[0016] Figure 1 is a schematic diagram of the cycle switching of the lower engagement (left) and the upper engagement (right) of the gear in the downhill shaking.

[0017] Figure 2 is a block diagram of the magnetic adsorption four-wheel trolley system of the present application.

[0018] Figure 3 is a schematic diagram of the stable state of the left wheel lower engagement and the right wheel upper engagement formed when the trolley is downhill according to the method of the present application.

[0019] Figure 4 is a force decomposition diagram of the trolley when the trolley is downhill according to the method of the present application.

[0020] Figure 5 is a comparison experiment diagram of the external encoder on the adsorption four-wheel trolley of the present application.

[0021] Figure 6 is a waveform diagram of the encoder output when the trolley shakes downhill before the method of the present application is adopted.

[0022] Figure 7 is a waveform diagram of the encoder output when the trolley smoothly goes downhill after the method of the present application is adopted. DETAILED DESCRIPTION

[0023] As Figure 1 shown, the wall climbing trolley in the prior art runs unstably and produces "stop-and-go" shaking problems under certain slope conditions when it travels downhill on a slope with a certain slope. The root cause of the problem lies in the interaction between the mechanical structure and the mechanical state. First, in order to ensure smooth gear transmission and prevent jamming, and due to the limitations of production and processing precision, there must be a certain engagement gap between the driving motor and the gear of the wheel. Secondly, the trolley is subjected to the force G along the slope, various friction forces (including dynamic friction f 动 and static friction f 静 , and f 静 >f动 That is, the force needed to push the trolley from rest to start moving is greater than the force needed to push it while it is moving, because in the rest state the static friction force needs to be overcome, while in the moving state only the smaller dynamic friction force needs to be overcome, plus the motor driving force F.

[0024] The chattering phenomenon usually occurs on slopes with a gravity component G between the static friction force f 静 and the dynamic friction force f 动 , i.e. under the condition f 动 <G< f 静 . Under this condition, the specific chattering process is as follows:

[0025] Rest start: Since G < f 静 , the trolley is at rest. To make it descend, the motor needs to provide a downward driving force F, so that G + F > f 静 , breaking the rest state. At this time, the motor gear and the wheel gear are in the "under engagement" state (the motor gear actively pushes the wheel gear).

[0026] Acceleration out of control: Once the trolley starts moving, the friction force suddenly changes from the larger static friction force f 静 to the smaller dynamic friction force f 动 . Since G > f 动 , even if the motor driving force F disappears, the gravity component G itself is enough to make the trolley accelerate downward.

[0027] Reverse braking: the motor rotates at a set uniform speed, while the trolley accelerates due to gravity, causing the wheel speed to exceed the motor speed. This makes the gear engagement state between the two rapidly pass through the gap and become the "over engagement" state (the motor gear reversely brakes the wheel gear). At this time, the motor generates an upward braking force F against the wheel, which together with the dynamic friction force f 动 forms a braking torque.

[0028] Stop and repeat: when the total upward resistance (f 动 + F) is greater than the downward gravity component G, the trolley decelerates and eventually stops. After stopping, the friction force again becomes the static friction force f 静 , the system returns to the initial rest state, and the motor continues to rotate, entering step 1 again, thus forming a "acceleration-braking-stop" periodic chattering.

[0029] The purpose of the present application is to provide a control method that can intelligently judge the working conditions, has low cost, simple control, and can fundamentally eliminate the chattering of the wall-climbing trolley descending a slope.

[0030] To achieve the above object, the application adopts the following technical scheme: a dolly control method for eliminating the shaking of a wall-climbing dolly when descending, the core of which is to apply differential torque control to the driving motors on both sides of the dolly to establish a stable counter torque to eliminate the influence of gear clearance.

[0031] As shown in Figure 2 The dolly system mainly includes a control module, a driving module (driver) and left and right motors for driving the left and right wheels respectively. Specifically, the left and right wheels are driven by different driving motors, and the driving motor for driving the left wheel is referred to as the left motor, and the driving motor for driving the right wheel is referred to as the right motor, and the driving of the two wheels on both sides is ensured to be synchronous; when the dolly is in a descending state, the maximum torque of one of the left motor and the right motor is limited to aT, where a<1, T is the maximum torque of the left motor and the right motor when the dolly is running normally, and the rotational speed is set to bV, where b>1, V is the rotational speed of the driving motor corresponding to the current speed of the dolly, and the other driving motor or group of driving motors is not changed, the maximum torque is set to T, and the rotational speed is set to V; at this time, the direction of the output torque of the driving motor with the maximum torque of aT is the same as the direction of its rotation; the direction of the output torque of the driving motor with the maximum torque of T is opposite to the direction of its rotation; in this way, the shaking that occurs during the descending process of the dolly can be eliminated, and stable driving of the dolly can be realized. Since the maximum torque of one side of the driving motor is smaller and the rotational speed is faster, the driving motor on this side will provide a downward force along the slope when the dolly is in a descending state, and in order to maintain the stable movement of the dolly, the driving motor on the other side will provide an upward force along the slope, and since the maximum torque of the driving motor on this side is larger, it will make the dolly move at a speed corresponding to the rotational speed of the driving motor on this side, while the driving motor on the other side with smaller maximum torque will be in a following state.

[0032] The core is to differentially control the left and right motors when the dolly is in a descending state. Assuming that the left motor is selected as the adjustment side and the right motor is selected as the reference side:

[0033] The left motor (adjustment side): the maximum torque is set to aT (a<1), and the target rotational speed is set to bV (b>1). Since the target rotational speed bV is higher than the actual speed V of the dolly, the motor will actively output torque to try to accelerate, so the "output torque direction is the same as the rotation direction", which plays a driving role. Its gear will form a "lower meshing" state with the wheel gear.

[0034] Right motor (reference side): maximum torque remains T, target speed remains V. Due to gravity G, the trolley has a tendency to accelerate beyond speed V. To maintain the speed at V, the motor controller will apply a braking torque, so its "output torque direction is opposite to the rotation direction", playing a braking role. Its gear will push the wheel gear in reverse, forming an "upper meshing" state.

[0035] The core difference between lower meshing and upper meshing lies in the contact mode of gear tooth surface and the direction of force transmission:

[0036] When the motor gear actively pushes the wheel gear to move (the driving side motor works when going downhill), the front tooth surface of the motor gear will tightly push against the rear tooth surface of the wheel gear, like 'pushing the front tooth with the rear tooth', the force direction is consistent with the wheel movement direction, which is "lower meshing";

[0037] When the motor gear needs to brake the wheel (the braking side motor works when going downhill), due to the tendency of the wheel to exceed the speed, the rear tooth surface of the motor gear will reversely push against the front tooth surface of the wheel gear, like 'pulling the rear tooth with the front tooth', the force direction is opposite to the wheel movement direction, which is "upper meshing".

[0038] The two states will cause shaking due to frequent switching of gear clearance, while the present application differentiates the control to make the two sides of the gear stable in 'lower meshing' and 'upper meshing' state respectively, and the tooth surface no longer slides in the clearance, so as to realize smooth driving. The present application forms a stable tension through one side driving (aT, bV) and one side braking (T, V), which essentially forces the gear clearance to be 'filled' through the continuous pushing force of the driving side and the continuous pulling force of the braking side, so that the gear is always in a no-gap fitting state, avoiding shaking caused by meshing state switching.

[0039] As for the speed difference (bV and V): it only exists in the starting stage (time t), the purpose is to quickly eliminate the gear clearance; by strictly limiting the value of a (F aT < f 动1 - G), it is ensured that the driving force of the driving side will not cause deviation. After t ends, the driving side returns to T, V, and the speed of the two sides returns to the same, ensuring straight-line driving.

[0040] Through this "one drive and one brake" setting, a stable tension is formed between the two sides of the wheel, effectively locking the meshing position of the gear (as Figure 3 shown), thereby eliminating the shaking caused by the reciprocating switching of the gear clearance.

[0041] In addition, in order to detect the moving state of the trolley, a gyroscope or other sensors can be used for detection, but this involves more coordinated control. Therefore, the embodiment provides another method for detecting the moving state of the trolley by detecting the output torque of the driving motor through the driver of the driving motor, and the method is as follows: when starting detection, the trolley is first controlled to brake; then the maximum torque of the driving motor on one side of the left motor and the right motor is set as aT, and the rotating speed is set as bV, aT and bV are consistent with aT and bV in claim 1, and the maximum torque of the driving motor on the other side is set as T, and the rotating speed is set as V; after the brake is released, the trolley is controlled to move in the original direction, and the torque of the left motor and the right motor is detected through the driver of the left motor and the right motor, specifically, the output torque of the motor is detected by detecting the size of the output current of the driver. When the maximum torque is set as T and the rotating speed is set as V, the torque of the driving motor on the side does not exceed the set value cT, wherein c < 1, at this time, the trolley is in a non-overloaded uphill state (that is, the trolley can be in a plane movement or a downhill movement or a small slope uphill), and at this time, the parameters of the driving motor do not need to be adjusted, so it is uniformly determined that the trolley is in a downhill state that needs to eliminate the jitter, and the set parameters of the left motor and the right motor are kept unchanged; if it is detected that the torque of the driving motor on the side where the maximum torque is set as T and the rotating speed is set as V is greater than the set value cT, it is considered that the trolley is in an overloaded uphill state (that is, the trolley is in a large slope uphill movement state), at this time, the trolley needs a larger driving force, so the maximum torque of the driving motor on the side where the maximum torque is set as aT and the rotating speed is set as bV is set as T and the rotating speed is set as V.

[0042] That is, the downhill judgment: if it is monitored that the torque of the right motor continuously decreases below a preset threshold cT (for example, c = 0.5), it is considered that the gravity helps the trolley to move, and the right motor only needs a small braking torque to maintain the speed. At this time, the system determines that the trolley is in a “downhill state that needs to eliminate jitter”, and the current differential parameter setting is kept unchanged.

[0043] The overloaded uphill judgment: on the contrary, if it is monitored that the torque of the right motor is greater than cT, it is considered that the trolley can be in an uphill or flat heavy load state, and the right motor needs a larger driving force to maintain the speed. At this time, the system determines that the trolley is in an “overloaded uphill state”, and there is no downhill jitter problem, so the differential control is not suitable, and the parameters of the left motor should be immediately restored to T and V, so that the two sides of the motor cooperatively provide the maximum driving force.

[0044] At the same time, in order to ensure the effective implementation of the technical scheme, the values of the key parameters should also be limited: the coefficient a must be accurately controlled to ensure that the driving force F aT converted from the torque aT) satisfies two conditions: (1) F aT>f 静 -G: The driving force must be sufficient to overcome the difference between the static friction force and the gravity component to start the car. (2) F aT <f 动1 -G: The driving force cannot be too large to prevent it from exceeding the longitudinal static friction of the wheel on the other side, causing the car to deviate or turn. Figure 4 As shown (analyzed from the following slope), F aT is the force generated by the maximum torque aT of the left wheel motor, f 动1 The kinetic friction force generated by the bearings and gears in the longitudinal direction is the force component. Since the left wheel's speed is set to be greater than the right wheel, the left wheel has a tendency to move relative to the right wheel, and the right wheel can be considered as the center of the movement circle. When F aT To a certain extent, F aT +G>f 动1 , will make the left wheel move faster than the right wheel, thus making the car turn. In order to ensure that the car can move in a straight line, F aT Must be less than f 动1 -G.

[0045] In practice, the value of a should ensure that the motor can just drive the gears to complete meshing, but not be sufficient to drive the car alone.

[0046] The coefficient b can be greater than 1. The larger the value, the faster the gear on the adjustment side reaches the meshing position. Generally, b=1.5 is sufficient for most application scenarios.

[0047] Differential control, however, does not need to be maintained throughout the entire process. It only needs to last for a brief period, t, during the startup phase to ensure a stable meshing state. This duration, t, must be greater than the time required for the gears to travel through the maximum meshing gap, d. This duration is calculated as: t > d / ((b-1)V), where V is the vehicle's designed minimum operating speed. After time t expires, the parameters of the adjustment-side motor can be restored to T and V. The established stable meshing state is maintained due to inertia, and the vehicle continues to travel smoothly.

[0048] In order to verify the effect of the present invention, a comparative experiment was carried out on a magnetic adsorption four-wheeled vehicle (such as Figure 5 Using an external encoder and oscilloscope, the uniformity of the wheel speed is monitored as the vehicle descends on a slope.

[0049] After the method is applied, the gears of the left and right motors can be ensured to be in the upper meshing state when driving upward. Before meshing, the torque feedback of the two motors is quite different; after stable meshing, the torque of the two motors is basically consistent, and they jointly provide stable driving force. When driving downward on a slope, one side of the wheel gears can be stably in the upper meshing state (braking side), and the other side of the wheel gears can be stably in the lower meshing state (driving side), and the whole driving process is stable and smooth without shaking.

[0050] Specifically, as shown in Figure 6 Without using the method of the application, the encoder output waveform repeatedly switches between dense pulses (acceleration) and no pulses (stop), which intuitively reflects the shaking phenomenon of the trolley.

[0051] After the method of the application is used: under the same working condition, the monitoring result (as shown in Figure 7 The waveform pulse interval of the encoder output is uniform and continuous during the whole downhill process, which indicates that the trolley speed is constant, the operation is stable and smooth, and there is no shaking phenomenon.

[0052] Of course, the above is only a preferred embodiment of the application, and is not intended to limit the use range of the application, so any equivalent change in the principle of the application should be included in the protection scope of the application.

Claims

1. A method for controlling a wall-climbing trolley to eliminate shaking when descending a slope, characterized by: The left and right wheels of the car are driven by different drive motors, the left motor drives the left wheel, and the right motor drives the right wheel; when the car is in a downhill state, the maximum torque of the drive motor on one of the left or right motors is limited to aT, where a < 1, T is the maximum torque of the left and right motors when the car is driving normally, and the rotation speed is set to bV, where b > 1, V is the corresponding rotation speed of the drive motor when the car is driven at the current speed; the other or a group of drive motors does not change, and the maximum torque is maintained at T and the rotation speed is V; wherein, the direction of the output torque of the drive motor with the maximum torque set to aT is the same as its rotation direction; the direction of the output torque of the drive motor with the maximum torque set to T is opposite to its rotation direction; thereby eliminating the jitter that occurs during the downhill process of the car and achieving smooth driving.

2. A method for controlling a wall-climbing vehicle to eliminate downhill shaking according to claim 1, characterized in that: The car detects whether it is in a downhill state by the following method: (1) When starting the test, first control the car brake; then set the maximum torque of the drive motor on one side of the left motor and the right motor to aT, and the rotation speed to bV, where aT and bV are consistent with aT and bV described in claim 1, and set the maximum torque of the drive motor on the other side to T, and the rotation speed to V; (2) After releasing the brake, the car is controlled to move in the original direction. At the same time, the torque of the left motor and the right motor are detected through the drivers of the left motor and the right motor. (3) When the maximum torque is set to T and the rotation speed is set to V, the torque of the drive motor on one side does not exceed the set value cT, where c < 1, then the car is considered to be in a downhill state where shaking needs to be eliminated, and the set parameters of the left and right motors remain unchanged.

3. A method for controlling a wall-climbing trolley to eliminate downhill shaking according to claim 2, characterized in that: When detecting whether the car is in a downhill state, if it is detected that the torque of the drive motor on the side with the maximum torque set to T and the rotation speed set to V is greater than the set value cT, the car is considered to be in an overloaded uphill state, and the maximum torque is set to aT, and the rotation speed is set to bV. The maximum torque of the drive motor on the side is set to T, and the rotation speed is set to V.

4. A method for controlling a wall-climbing trolley to eliminate downhill shaking according to any one of claims 1 to 3, characterized in that: The value of a satisfies the following conditions: (1) F aT >f 静 -G, where F aT is the driving force corresponding to aT, f 静 is the static friction between the bearing and the gear at rest, G is the downward component of gravity along the slope; (2) F aT <f 动1 -G, where f 动1 It is the longitudinal component of the kinetic friction between the bearing and the gear during movement; and the value of a can only drive the gear to engage but not drive the trolley to move.

5. A method for controlling a wall-climbing trolley to eliminate downhill shaking according to any one of claims 1 to 3, characterized in that: The value of b is b>1, so as to shorten the time from the start of gear rotation to engagement.

6. A method for controlling a wall-climbing trolley to eliminate downhill shaking according to any one of claims 1 to 3, characterized in that: In the downhill state, the wheel gear on the side with the maximum torque of aT and the rotation speed of bV is in the lower meshing state, and the wheel gear on the side with the maximum torque of T and the rotation speed of V is in the upper meshing state, and the meshing state of the gears on both sides remains stable.

7. A method for controlling a wall-climbing trolley to eliminate downhill shaking according to any one of claims 1 to 3, characterized in that: After executing the control method of claim 1, the parameter setting duration t is maintained, where t>d / ((b-1)V), d is the maximum gap between the magnetic wheels, and V is the minimum speed of the trolley. Subsequently, the motor originally set to aT and bV is restored to the maximum torque T and rotation speed V, so that the parameters of the motors on both sides are consistent.

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