Control system for downhill operation and aerial platform

Abstract

The application relates to the technical field of engineering machinery, and discloses a control system for downhill working conditions and an aerial work platform. The control system comprises a voltage detection device, an energy storage device, a first switch device, and a control device. The control device is used for controlling the first switch device to turn on the circuit of the energy storage device to capture feedback current when the DC bus voltage is equal to or greater than a first preset voltage, and controlling the first switch device to turn on the circuit of the energy storage device to supply power to the driver when the DC bus voltage is less than or equal to a second preset voltage. The application can intervene in the control strategy, capture feedback current to reduce the feedback voltage of the driver when there is a risk of stalling, and supply power to the driver by the absorbed feedback energy when the vehicle speed is reduced, so that the braking torque can be prevented from becoming small, the occurrence of the downhill stalling risk can be effectively inhibited, and smooth parking can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engineering machinery, in particular to a control system for downhill working condition and a high-altitude working vehicle. BACKGROUND

[0002] The running system of an electrically driven high-altitude working vehicle (self-propelled) usually has no running brake, and its running deceleration and parking rely on energy feedback type regenerative braking technology, and parking relies on electromagnetic braking or hydraulic braking. Such a braking mode has a risk: when downhill, if the regenerative braking voltage exceeds the protection voltage of the driver, the braking torque will be limited (i.e., the strength of regenerative braking will be weakened), thereby making the high-altitude working vehicle have the risk of stalling. At this time, if the vehicle is parked through the emergency stop switch, the parking brake will directly lock the brake, forcing the high-altitude working vehicle to slide. On the one hand, the high-speed locking of the brake is harmful to the brake, and on the other hand, the braking distance may be longer. Moreover, even after the vehicle speed is reduced, the DC bus voltage of the driver may be lower than the minimum working voltage of the driver, thereby causing the parking brake to directly lock the brake, which is harmful to the parking brake to a great extent. SUMMARY

[0003] The purpose of the present application is to provide a control system for downhill working condition and a high-altitude working vehicle, which can intervene in the control strategy when the DC bus voltage exceeds a first preset voltage (e.g., a certain voltage less than the protection voltage of the driver) (i.e., before the downhill overspeed occurs), and reduce the DC bus voltage of the driver by capturing the feedback current, thereby avoiding the decrease of the braking torque, so as to effectively inhibit the occurrence of the downhill stalling risk, and can supply power to the driver by the captured feedback energy when the DC bus voltage is lower than a second preset voltage (e.g., a certain voltage greater than the minimum working voltage of the driver), so as to achieve smooth parking.

[0004] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a control system for downhill working condition, comprising: a voltage detection device for detecting the DC bus voltage of a driver; an energy storage device for capturing the feedback current delivered by the driver; a first switch device for turning on a first circuit in which the energy storage device is located; and a control device for performing the following operations: in the case that the DC bus voltage is equal to or greater than a first preset voltage, the first circuit is turned on by controlling the first switch device, so that the feedback current is captured by the energy storage device, wherein the first preset voltage is less than the protection voltage of the driver; and in the case that the DC bus voltage is less than or equal to a second preset voltage, the first circuit is turned on by controlling the first switch device, so that the driver is powered by the energy storage device, wherein the first preset voltage is greater than the second preset voltage.

[0005] Preferably, the first preset voltage is less than a protection voltage of the driver.

[0006] Preferably, the second preset voltage is greater than a minimum working voltage of the driver.

[0007] Preferably, the control system further comprises an energy consumer and a second switching device for conducting a second circuit in which the energy consumer is located, and the control device is further configured to, in the case that the first energy storage is in a saturated state, control the first switching device to cut off the first circuit and control the second switching device to conduct the second circuit, so as to capture the feedback current by the energy consumer.

[0008] Preferably, the first switching device is a first high-frequency switch and the second switching device is a second high-frequency switch.

[0009] Preferably, the control device is configured to control the first switching device to conduct the first circuit by controlling a duty cycle of the first high-frequency switch, so as to control a speed of capturing the feedback current by the energy storage, and the control device is configured to control the second switching device to conduct the second circuit by controlling a duty cycle of the second high-frequency switch, so as to control a speed of capturing the feedback current by the energy consumer.

[0010] Preferably, the first high-frequency switch and the second high-frequency switch are field effect transistors, and the energy storage is a capacitor or a battery, and the energy consumer is a resistor.

[0011] By the above technical solution, the application firstly detects a DC bus voltage of a driver by a voltage detection device; then captures a feedback current delivered by the driver by an energy storage; then conducts a first circuit in which the energy storage is located by a first switching device; and finally, in the case that the DC bus voltage is equal to or greater than a first preset voltage (for example, a voltage less than a protection voltage of the driver), the control device controls the first switching device to conduct the first circuit, so as to capture the feedback current by the energy storage. Thus, the application can intervene in a control strategy when the DC bus voltage exceeds the first preset voltage (for example, a voltage less than the protection voltage of the driver) (i.e., before a downhill overspeed occurs), and reduce the DC bus voltage of the driver by capturing the feedback current, so as to avoid a decrease in braking torque, thereby effectively inhibiting the occurrence of a downhill speed loss risk, and the captured feedback energy can be used to supply power to the driver when the DC bus voltage is less than a second preset voltage (for example, a voltage greater than a minimum working voltage of the driver), so as to achieve a smooth stop.

[0012] The second aspect of the present application provides a high-altitude operation vehicle, which comprises the control system for downhill working condition.

[0013] Preferably, the high-altitude operation vehicle further comprises a parking brake and a driver for controlling the parking brake to brake when the rotating speed of the motor is less than a preset rotating speed.

[0014] Other features and advantages of the present application will be described in detail in the following detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application and explain the principles of the present application together with the detailed description below, but are not intended to limit the present application. In the drawings:

[0016] Figure 1 is a schematic diagram of a driving system comprising a control system according to an embodiment of the present application;

[0017] Figure 2 is a schematic diagram of a control system for downhill working condition according to an embodiment of the present application; and

[0018] Figure 3 is a schematic diagram of a control system for downhill working condition according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0020] Before introducing the specific embodiments of the present application, two concepts will be briefly described.

[0021] Regenerative braking: when the electric vehicle brakes, the (walking) motor can be controlled to operate as a generator, so as to convert the kinetic energy or potential energy of the vehicle into electrical energy and store it in the energy storage module.

[0022] Feedback current: during the regenerative braking process, the driver converts the electrical energy generated by the (walking) motor into a current that can be used by the energy storage module or other energy-consuming elements. This current is called feedback current.

[0023] Figure 2 is a schematic diagram of a control system (i.e. safety protection device) for downhill working condition according to an embodiment of the present application. As Figure 2As shown, the control system can include: a voltage detection device 10 for detecting the DC bus voltage of the driver; an energy storage device 20 for capturing the feedback current delivered by the driver; a first switching device 30 for conducting the first circuit in which the energy storage device 20 is located; and a control device 40 for, in the case where the DC bus voltage is equal to or greater than a first preset voltage, conducting the first circuit by controlling the first switching device 30 to capture the feedback current by the energy storage device 20; and in the case where the DC bus voltage is less than or equal to a second preset voltage, conducting the first circuit by controlling the first switching device to supply power to the driver by the energy storage device 20.

[0024] When the aerial work platform is descending, the motor works in the generator state to keep the vehicle speed unchanged, at which time the driver will generate a relatively high feedback electromotive force. Under normal circumstances, the driver will charge the battery, and the feedback electromotive force will not exceed the driver protection voltage.

[0025] The inventor found that, during the operation of the aerial work platform, if the battery cannot be charged (the battery is fully charged, the battery power map is limited, the line is faulty, the battery management system (BMS) is faulty, etc.), the feedback electromotive force will quickly reach the driver protection voltage. In order to avoid the power electronic device being destroyed by high voltage, the driver reduces the feedback braking strength, resulting in insufficient braking torque, and the vehicle speed may become faster and faster, and the equipment has the risk of losing control. If the operator reduces the speed by the speed control handle at this time, since the feedback braking strength of the driver is limited and cannot achieve the effect of speed reduction, the driver will control the parking brake to directly brake the brake after a certain period of time (usually 5S). If the operator stops the vehicle by the emergency stop switch at this time, the parking brake will directly brake the brake, forcing the equipment to slide. Both cases force the parking brake to brake at high speed. This high-speed brake mode, on the one hand, causes great damage to the brake, resulting in the risk that the aerial work platform cannot be parked on the slope; on the other hand, the sliding causes the braking distance to be possibly lengthened, the lateral stability to be deteriorated, and the aerial work platform to have the risk of collision and side slip.

[0026] For example, if the battery system cannot supply power to the driver 2 and the motor 100 and cannot be charged when descending. At this time, as shown in FIG. 2, the feedback electromotive force of the driver 2 will exceed the protection voltage of the driver 2, and the driver 2 will be damaged. In order to avoid the damage of the driver 2, the control device 40 controls the first switching device 30 to conduct the first circuit, so that the energy storage device 20 captures the feedback current of the driver 2, and the driver 2 is powered by the energy storage device 20. Figure 1As shown, the vehicle control unit (VCU) 90 and battery management system (BMS), powered by the battery 110, still function normally. After receiving the status information from the BMS and performing fault diagnosis, the VCU 90 issues a stop command and warning message, thereby keeping the relay K1 enabling the driver 2 in the closed state. As a result, the motor 100 transitions from motoring to regenerative braking. The electrical energy generated by regenerative braking can sustain the normal operation of the driver 2, and is far greater than the energy consumption required for normal operation. Because the battery cannot be charged, the DC bus voltage of the driver 2 will rise rapidly (i.e., the vehicle will stall when going downhill).

[0027] Therefore, during the operation of an aerial work platform vehicle, whether the battery is fully charged, the battery power map is limited, or there is a battery malfunction, the DC bus voltage of the driver may increase, which may cause the vehicle to stall when going downhill.

[0028] Wherein, the first preset voltage is greater than the second preset voltage.

[0029] Specifically, the first preset voltage is less than the protection voltage of the driver. For example, if the protection voltage of the driver is 100V, the first preset voltage can be set to be less than 100V (for example, the first preset voltage is 95V).

[0030] The second preset voltage is greater than the minimum operating voltage of the driver 2. In practical applications, the second preset voltage can be reasonably set according to specific circumstances, and it can be slightly greater than the minimum operating voltage (i.e., the lowest voltage when the driver is working normally).

[0031] The voltage detection device 10 can be a voltmeter 11, such as... Figure 3 As shown.

[0032] The first switching device 30 may be a first high-frequency switch 31. Further, the first high-frequency switch 31 may be a field-effect transistor (i.e., a MOSFET). Specifically, the control device 40 is used to turn on the first circuit by controlling the first switching device 30 by controlling the duty cycle of the first high-frequency switch 31 to control the rate at which the energy storage device 20 captures the feedback current.

[0033] The control device 40 is a central processing unit (CPU) 41, such as... Figure 3 As shown.

[0034] The energy storage device 20 may be a capacitor 21 (e.g., Figure 3 (as shown) or batteries, etc.

[0035] Specifically, the energy storage device 20 is used as the capacitor 21 (e.g.Figure 3 For example, when the DC bus voltage displayed by the voltmeter 11 is equal to or greater than a first preset voltage (for example, 95 V), that is, there is a risk of stalling, the CPU 41 controls the duty ratio of the first high-frequency switch 31 to turn on the circuit in which the capacitor 21 is located, so as to control the speed of the feedback braking energy absorbed by the capacitor, thereby controlling the feedback energy absorbed by the capacitor, and further stabilizing the DC bus voltage (that is, the feedback voltage) to prevent it from exceeding the protection voltage. At this time, since the driver will not limit the strength of the feedback braking (that is, enough braking torque can be provided), the corresponding vehicle speed becomes slower and slower, thereby avoiding the risk of stalling.

[0036] When the electric vehicle is downhill and stalls, the gravitational potential energy change on the downhill is usually absorbed by the mechanical brake, but the aerial work vehicle has no mechanical brake and can only rely on the battery charging to absorb. The absorption mode of the energy storage device designed in the embodiment solves the problem that the battery system cannot absorb due to failure or other reasons. By stabilizing the DC bus voltage, the problem that the driver loses power supply due to battery system failure or other reasons is solved, and the problem that the overvoltage alarm of the driver is caused by the overhigh feedback braking electromotive force is prevented.

[0037] In the embodiment, when the DC bus voltage displayed by the voltmeter 11 is equal to or greater than a first preset voltage (that is, there is a risk of stalling), the feedback braking energy is absorbed by the capacitor, so that the DC bus voltage (that is, the feedback voltage) of the driver can be controlled to be lower than the protection voltage of the driver. At this time, since the driver will not limit the strength of the feedback braking, the speed of the aerial work vehicle can be controlled to be slower and slower. However, after the DC bus voltage decreases (that is, the vehicle speed decreases), the DC bus voltage may be lower than the minimum working voltage of the driver, thereby causing the parking brake to directly engage the brake, which has a certain degree of damage to the parking brake.

[0038] In view of the above defects, in the embodiment, after the DC bus voltage decreases (that is, the vehicle speed decreases), the feedback braking energy absorbed by the energy storage device (for example, the capacitor 21) can also be used to power the driver, thereby avoiding the parking brake controlled by the driver from directly engaging the brake.

[0039] Specifically, in the above embodiment, the CPU 41 controls the duty ratio of the first high-frequency switch 31 to turn on the circuit in which the capacitor 21 is located, so as to control the speed of the feedback braking energy absorbed by the capacitor, thereby controlling the feedback energy absorbed by the capacitor. During the process of decreasing the DC bus voltage (that is, decreasing the vehicle speed), when the DC bus voltage displayed by the voltmeter 11 is less than or equal to a second preset voltage, the circuit in which the capacitor 21 is located is turned on by controlling the first high-frequency switch 31 (which is equivalent to a contactor), so as to power the driver 2 by the capacitor 21, thereby smoothly reducing the corresponding vehicle speed. When the motor 100 rotates at a speed lower than a certain value (for example, 30 rpm), the parking brake engages the brake.

[0040] On the basis of the above-mentioned embodiments, the control system can further comprise: an energy consumer; and a second switching device for conducting a second circuit in which the energy consumer is located.

[0041] Correspondingly, the control device is further configured to, in the case that the energy storage is in a saturated state, control the first switching device to cut off the first circuit and control the second switching device to conduct the second circuit, so as to capture the feedback current by the energy consumer.

[0042] The energy consumer can be a resistor 50, as shown in Figure 3 .

[0043] The second switching device can be a second high-frequency switch 32 (which can be a field effect transistor, i.e., a MOS tube), as shown in Figure 3 . Specifically, the control device 40 is configured to control the second circuit to be conducted by controlling the second switching device includes controlling the second circuit to be conducted by controlling the duty cycle of the second high-frequency switch, so as to control the speed of capturing the feedback current by the energy consumer

[0044] Specifically, in the case that the capacitor 21 is in a saturated state, the first circuit is cut off by controlling the first high-frequency switch 31, and the circuit in which the second high-frequency switch 32 is located is conducted by controlling the duty cycle of the second high-frequency switch, so as to control the speed of capturing the feedback current by the resistor 50, thereby controlling the feedback energy absorbed by the resistor, as shown in Figure 3 . In this way, the resistor 50 is only enabled after the energy storage capacitor is saturated, for consuming the excess feedback braking energy.

[0045] In an embodiment, the control system further comprises: a digital-to-analog converter 70, configured to convert the analog signal of the DC bus voltage detected by the voltage detection device 10 into a digital signal, and output the converted digital signal of the DC bus voltage to the control device 40, as shown in Figure 2 .

[0046] The overspeed control mode based on the DC bus voltage of each of the above embodiments can realize the downhill control of the vehicle. The control mode has the function of stall protection, which does not need to detect the speed of the vehicle and does not participate in the speed control, but ensures that the driver can maximize the braking capacity of the motor by stabilizing the DC bus voltage, thereby preventing the overspeed of the vehicle. Since the vehicle will not overspeed, it is less likely to stall. Therefore, during the operation of the aerial work vehicle, whether the battery is full, the battery power map is limited, or the DC bus voltage of the driver is high (or downhill stall) due to battery failure, the overspeed control based on the DC bus voltage is inhibited from the source, thereby effectively preventing the occurrence of downhill stall risk.

[0047] In summary, the application creatively first detects the DC bus voltage of the driver by the voltage detection device; then captures the feedback current delivered by the driver by the energy storage device; then turns on the first circuit in which the energy storage device is located by the first switching device; and finally performs the following operations by the control device: in the case that the DC bus voltage is equal to or greater than the first preset voltage, the first circuit is turned on by controlling the first switching device to capture the feedback current by the energy storage device, and in the case that the DC bus voltage is less than or equal to the second preset voltage, the first circuit is turned on by controlling the first switching device to supply power to the driver by the energy storage device. Thus, the application can intervene in the control strategy when the DC bus voltage exceeds the first preset voltage (for example, a voltage less than the protection voltage of the driver) (i.e., before the downhill overspeed occurs), and reduce the DC bus voltage of the driver by capturing the feedback current, thereby avoiding the decrease of the braking torque, effectively inhibiting the occurrence of downhill stall risk, and supplying power to the driver by the captured feedback energy when the DC bus voltage is lower than the second preset voltage (for example, a voltage greater than the minimum working voltage of the driver), to realize smooth parking.

[0048] An embodiment of the application also provides a high-altitude work vehicle, which can include the control system (i.e., safety protection device) for downhill working conditions.

[0049] The high-altitude work vehicle can also include a parking brake 120 and a driver 2 for controlling the parking brake 120 to brake when the speed of the motor is less than a preset speed.

[0050] In an embodiment, the high-altitude work vehicle can also include a battery 80, a vehicle control unit (VCU) 90, a motor 100, a speed reducer 130, a wheel 140, and a DC / DC converter 150, etc. Figure 2As shown. Among them, the battery 80 is configured with a battery management system (BMS), and the vehicle control unit (VCU) 90 exchanges information with the BMS through the CAN bus. The VCU 90 can adjust the target speed of the motor 100 according to the battery state and fault information sent by the BMS.

[0051] Specifically, the feedback current generated by regenerative braking is captured by the control system for downhill working condition. Since the driver 2 does not limit the strength of the feedback braking, the motor 100 can realize the speed reduction control of the wheel 140 through the speed reducer 130, so that the vehicle speed is lower and lower. And in the case that the speed of the motor 100 is less than the preset speed, the parking brake is controlled to brake to realize smooth parking. Therefore, in the case of failure of the driving system, the embodiment can adopt the mode of speed reduction and brake holding, which can reduce the damage to the parking brake as much as possible, thereby prolonging the service life of the parking brake.

[0052] The above embodiment can absorb the energy generated by feedback braking through the capacitor, and control the vehicle speed to reduce in time. When the feedback energy is insufficient, the feedback electric energy absorbed by the energy storage capacitor is supplemented in time to maintain the normal work of the driver, until the complete parking. Thus, it can ensure that the parking brake is not damaged by dynamic impact energy, which can greatly reduce the probability of high-speed brake holding, prolong the service life of the parking brake, and reduce the risk of hill parking and sliding, thereby realizing safer and more reliable downhill.

[0053] The specific details and benefits of the aerial work platform provided by the embodiment of the application can be referred to the description of the feedback current control device above, which will not be described here.

[0054] The preferred embodiments of the application are described in detail above in combination with the drawings, but the application is not limited to the specific details in the above embodiments. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, and these simple modifications all belong to the protection scope of the application.

[0055] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again by the application.

[0056] In addition, various different embodiments of the application can also be combined in any appropriate manner, as long as they do not deviate from the idea of the application, and they should be considered as disclosed by the application.

Claims

1. A control system for downhill operation, characterized in that The control system is applied to an aerial work platform, and the control system comprises: a voltage detection device configured to detect a DC bus voltage of a drive; an energy storage device configured to capture a feedback current delivered by the drive; a first switch device configured to turn on a first circuit in which the energy storage device is located; and a control device configured to: in a case where the DC bus voltage is equal to or greater than a first preset voltage, turn on the first circuit by controlling the first switch device, so as to capture the feedback current by the energy storage device; and in a case where the DC bus voltage is less than or equal to a second preset voltage, turn on the first circuit by controlling the first switch device, so as to supply power to the drive by the energy storage device, to avoid the parking brake from being directly locked due to the DC bus voltage of the drive being lower than a minimum working voltage of the drive.

2. The control system of claim 1, wherein, The first preset voltage is greater than the second preset voltage, the first preset voltage is less than a protection voltage of the drive, and the second preset voltage is greater than the minimum working voltage of the drive. The control system further comprises: an energy consumer; and a second switch device configured to turn on a second circuit in which the energy consumer is located, 3. The control system of claim 2, wherein, Correspondingly, the control device is further configured to, in a case where the first energy storage device is in a saturated state, turn off the first circuit by controlling the first switch device, and turn on the second circuit by controlling the second switch device, so as to capture the feedback current by the energy consumer.

4. The control system of claim 3, wherein, The first switch device is a first high-frequency switch, and the second switch device is a second high-frequency switch.

5. The control system of claim 3, wherein, The control device is configured to turn on the first circuit by controlling the first switch device, including turning on the first circuit by controlling a duty cycle of the first high-frequency switch, so as to control a speed of capturing the feedback current by the energy storage device, and the control device is configured to turn on the second circuit by controlling the second switch device, including turning on the second circuit by controlling a duty cycle of the second high-frequency switch, so as to control a speed of capturing the feedback current by the energy consumer.

6. The control system of claim 2, wherein, The first high-frequency switch and the second high-frequency switch are field effect transistors.

7. An aerial work platform, characterized in that The energy storage device is a capacitor or a battery, and the energy consumer is a resistor.

8. The aerial work platform vehicle of claim 7, wherein, The aerial work platform comprises the control system for downhill working conditions according to any one of claims 1-6. The aerial work platform further comprises: a parking brake; and a drive configured to control the parking brake to brake in a case where a rotational speed of a motor is less than a preset rotational speed.

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