CN116461332A

CN116461332A - Control system for downhill working condition and overhead working truck

Info

Publication number: CN116461332A
Application number: CN202211091407.0A
Authority: CN
Inventors: 任会礼; 朱后; 熊路; 岳泽擎; 柳权
Original assignee: Hunan Zoomlion Intelligent Aerial Work Machinery Co Ltd
Current assignee: Hunan Zoomlion Intelligent Aerial Work Machinery Co Ltd
Priority date: 2022-09-07
Filing date: 2022-09-07
Publication date: 2023-07-21

Abstract

The invention relates to the technical field of engineering machinery, and discloses a control system for downhill working conditions and an overhead working truck. The control system includes: the voltage detection device is used for detecting the direct current bus voltage of the driver; the first current capturing device is used for capturing feedback current transmitted by the driver; a first switching device for turning on a first circuit in which the first current capturing device is located; and a control device for controlling the first switch device to conduct the first circuit so as to capture the feedback current by the first current capture device when the DC bus voltage is equal to or greater than a first preset voltage. The invention can be inserted into a control strategy, and the DC bus voltage of the driver is reduced by capturing feedback current, so that the braking moment is prevented from becoming smaller, and the occurrence of downhill stall risk is effectively restrained.

Description

Control system for downhill working condition and overhead working truck

Technical Field

The invention relates to the technical field of engineering machinery, in particular to a control system for downhill working conditions and an overhead working truck.

Background

Electrically driven overhead vehicles (self-propelled) typically have no service brakes, and both deceleration and stopping rely on energy-regenerative braking technology, either electromagnetic or hydraulic braking. This braking mode presents a risk: on downhill slopes, if the regenerative braking voltage exceeds the protection voltage of the drive, the braking torque is limited (i.e. the strength of the regenerative braking is reduced), so that the aerial vehicle is at risk of stalling. At this time, if the vehicle is parked by the emergency stop switch, the parking brake can directly band-type brake to force the aerial working vehicle to slide. High-speed band-type brakes on one hand have great damage to the brakes, and on the other hand the braking distance may become longer.

Disclosure of Invention

The invention aims to provide a control system for downhill working conditions and an overhead working truck, which can intervene in a control strategy when the voltage of a direct current bus exceeds a first preset voltage (for example, a certain voltage smaller than the protection voltage of a driver) (namely, before the occurrence of downhill overspeed), and the voltage of the direct current bus of the driver is reduced by capturing feedback current, so that the braking moment is prevented from becoming smaller, and the occurrence of downhill stall risk is effectively restrained.

To achieve the above object, a first aspect of the present invention provides a control system for a downhill operation, the control system including: the voltage detection device is used for detecting the direct current bus voltage of the driver; the first current capturing device is used for capturing feedback current transmitted by the driver; a first switching device for turning on a first circuit in which the first current capturing device is located; and a control device for controlling the first switch device to conduct the first circuit so as to capture the feedback current by the first current capture device when the DC bus voltage is equal to or greater than a first preset voltage.

Preferably, the first preset voltage is smaller than a protection voltage of the driver.

Preferably, the first current capture device is an energy store and/or an energy consumer.

Preferably, in the case where the first current capturing device is the energy storage device, the control system further includes: a second current capture device; and a second switching device for turning on a second circuit in which the second current capturing device is located, and correspondingly, the control device is further configured to, when the energy storage is in a saturated state, turn off the first circuit by controlling the first switching device, and turn on the second circuit by controlling the second switching device, so as to capture the feedback current by the second current capturing device.

Preferably, the first switching means is a first high frequency switch and the second switching means is a second high frequency switch.

Preferably, the first high frequency switch and the second high frequency switch are field effect transistors.

Preferably, the control means for conducting the first circuit by controlling the first switching means comprises: switching on the first circuit by controlling the duty cycle of the first high frequency switch to control the speed at which the feedback current is captured by the first current capture means, and the control means for switching on the second circuit by controlling the second switching means comprises: the second circuit is turned on by controlling the duty cycle of the second high frequency switch to control the speed at which the feedback current is captured by the second current capture device.

Preferably, the second current capture device is an energy store and/or an energy consumer.

Through the technical scheme, the direct current bus voltage of the driver is creatively detected through the voltage detection device; then capturing feedback current transmitted by the driver through a first current capturing device; and then, under the condition that the voltage of the direct current bus is equal to or greater than a first preset voltage, the control device controls the first switching device to conduct the first circuit so as to capture the feedback current by the first current capturing device. Therefore, the invention can intervene in the control strategy when the DC bus voltage exceeds a first preset voltage (for example, a certain voltage smaller than the protection voltage of the driver) (i.e. before the occurrence of downhill overspeed), and the DC bus voltage of the driver is reduced by capturing the feedback current, so that the brake moment is prevented from becoming smaller, and the occurrence of the risk of downhill stall is effectively restrained.

A second aspect of the present invention provides an aerial work vehicle comprising: the control system is used for downhill working conditions.

Preferably, the aerial vehicle further comprises: a parking brake; and the driver is used for controlling the parking brake to brake under the condition that the rotating speed of the motor is smaller than the preset rotating speed.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate the invention and together with the description serve to explain, without limitation, the invention. In the drawings:

FIG. 1 is a schematic diagram of a control system for downhill operating conditions provided in an embodiment of the present invention;

FIG. 2 is a schematic diagram of a travel drive system including a control system according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a control system for downhill operating conditions provided in accordance with an embodiment of the present invention; and

FIG. 4 is a schematic diagram of a control system for downhill operation according to an embodiment of the present invention.

Detailed Description

The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.

Before describing the embodiments of the present invention, two concepts will be briefly described.

Regenerative braking: when the electric vehicle is braked, the (walking) motor can be controlled to operate as a generator, so that kinetic energy or potential energy of the vehicle is converted into electric energy and stored in the energy storage module.

Feedback current: during regenerative braking, the drive converts the electrical energy generated by the (travelling) motor into electrical current, known as feedback current, that is available to the energy storage module or other energy consuming components.

FIG. 1 is a schematic diagram of a control system (i.e., safety protection device) for downhill operation according to one embodiment of the present invention. As shown in fig. 1, the control system 1 may include: voltage detection means 10 for detecting a dc bus voltage of the driver; first current capturing means 20 for capturing a feedback current delivered by the driver; a first switching device 30 for conducting a first circuit in which the first current capturing device 20 is located; and a control device 40 for controlling the first switching device 30 to conduct the first circuit to capture the feedback current by the first current capturing device 20 when the dc bus voltage is equal to or greater than a first preset voltage.

When the overhead working truck descends, the motor works in a generator state to keep the speed of the truck unchanged, and at the moment, the driver can generate relatively high feedback electromotive force. Normally, the driver charges the battery, and the feedback electromotive force does not exceed the driver protection voltage.

The inventor researches and discovers that if the battery cannot be charged (the battery is full, the battery power Map (Map) is limited, the line is faulty, the Battery Management System (BMS) is faulty, etc.) during the operation of the aerial working vehicle, the feedback electromotive force can rapidly reach the driver protection voltage. In order to avoid the power electronics being destroyed by high pressure, the driver reduces the strength of the feedback brake, resulting in insufficient braking torque, possibly faster and faster vehicle speeds, and the equipment is at risk of runaway. If the operator is at this moment slowed down by the speed control handle, the driver can control the parking brake to brake directly after a certain time (usually 5S) because the feedback braking strength of the driver is limited and cannot achieve the speed reduction effect. If the operator parks through the scram switch at this moment, the parking brake can directly band-type brake, forces equipment to slide. Both cases force the parking brake to brake at high band-type brake speeds. The high-speed band-type brake braking mode has larger damage to the brake, so that the risk of incapability of parking on a slope exists in the overhead working truck; on the other hand, the braking distance may be long due to sliding, lateral stability is poor, and the overhead working truck is at risk of collision and sideslip.

For example, when going downhill, the battery system may not be able to supply power to the drive 2 and the motor 100 nor to charge the battery system. At this time, as shown in fig. 2, the Vehicle Controller (VCU) 90 and the Battery Management System (BMS) powered by the battery 110 still can work normally, and after receiving the state information provided by the BMS and performing fault judgment, the VCU 90 sends out a parking instruction and warning information, so as to control the relay K1 enabled by the driver 2 to be still in a closed state, thereby, the motor 100 enters a feedback braking state from an electric state, and the electric energy generated by the feedback braking can maintain the normal work of the driver 2 and is far greater than the energy consumption required by the normal work of the driver 2. The dc bus voltage of the drive 2 may rise rapidly (i.e. the vehicle may stall downhill) due to the inability to charge the battery.

Therefore, during the operation of the overhead working truck, the dc bus voltage of the driver may be raised, either due to the full battery power, the limitation of the battery power Map (Map), or the battery failure, and thus the vehicle may stall downhill.

The first preset voltage is smaller than the protection voltage of the driver. If the protection voltage of the driver is 100V, the first preset voltage may be set to be less than 100V (e.g., the first preset voltage is 95V).

The voltage detection device 10 may be a voltmeter 11, as shown in fig. 3.

Wherein, the first switch device 30 may be a first high frequency switch 31, as shown in fig. 3. Further, the first high frequency switch 31 may be a field effect transistor (e.g., moS transistor). Specifically, the controlling means 40 for conducting the first circuit by controlling the first switching means 30 comprises: the first circuit is turned on by controlling the duty cycle of the first high frequency switch 31 to control the speed at which the feedback current is captured by the first current capture device 20.

The control device 40 is a Central Processing Unit (CPU) 41, as shown in fig. 3 or fig. 4.

Specifically, in the case where the dc bus voltage shown in the voltmeter 11 is equal to or greater than a first preset voltage (for example, 95V), the CPU 41 controls the first current capture device 20 (for example, an energy storage and/or an energy consumer) to capture the feedback current by controlling the duty ratio of the first high-frequency switch 31, so as to control the speed at which the first current capture device 20 absorbs the feedback energy, thereby controlling the feedback energy absorbed by the first current capture device 20, and further controlling the dc bus voltage (i.e., the feedback voltage) of the driver to be lower than the protection voltage of the driver. At this time, since the actuator does not limit the intensity of the feedback brake, the speed of the overhead working truck can be controlled more and more slowly.

When the electric automobile stalls downhill, the change of gravitational potential energy of the downhill is absorbed through a mechanical brake, but the aerial working automobile does not have the mechanical brake and can only be absorbed by depending on battery charging. The absorption mode of the current capture device designed by the scheme solves the problem that the battery system fails and the like cannot be absorbed. By means of stabilizing the direct-current bus voltage, the problem that a driver loses power due to the fact that a battery system is in fault and the like is solved, and overvoltage alarm of the driver caused by too high feedback braking electromotive force is prevented.

The control system is explained and illustrated in detail below from the point of view of the first type of embodiment (the first current capturing device 20 is an energy storage device) and the second type of embodiment (the first current capturing device 20 is an energy consumer), respectively.

In a first class of embodiments, the first current capture device 20 may be an energy storage device. The energy storage device may be a capacitor 21 (as shown in fig. 3) or a storage battery.

Specifically, when the dc bus voltage shown by the voltmeter 11 is equal to or greater than the first preset voltage (i.e., there is a stall risk), the CPU 41 controls the duty ratio of the high-frequency switch 31 to turn on the circuit in which the capacitor 21 is located, so as to control the speed at which the capacitor absorbs the feedback braking energy, thereby controlling the feedback energy absorbed by the capacitor, and further stabilizing the dc bus voltage to prevent it from exceeding the protection voltage. At this point, since the driver does not limit the strength of the feedback brake (i.e., can provide sufficient braking torque), the corresponding vehicle speed is getting slower and slower, thereby avoiding the risk of stall.

That is, when there is a stall risk, the energy storage capacitor absorbs feedback braking energy to stabilize the dc bus voltage. In the case where the first current capture device 20 is the energy storage device, the control system may further include: a second current capture device; and a second switching device for conducting a second circuit in which the second current capturing device is located.

Correspondingly, the control device is further configured to turn off the first circuit by controlling the first switching device and turn on the second circuit by controlling the second switching device to capture the feedback current by the second current capturing device when the energy storage is in a saturated state.

Wherein the second current capture device may be an energy consumer (e.g., resistor 50) and/or an energy store (e.g., capacitor); and the second switching means may be a second high frequency switch 32 (which may be a field effect transistor, i.e. MoS transistor), as shown in fig. 3.

Specifically, in the case where the capacitor 21 is in a saturated state, the first circuit is turned off by controlling the first high frequency switch 31, and the second circuit in which the second high frequency switch 32 is located is turned on by controlling the duty ratio thereof, so as to control the speed at which the feedback current is captured by the resistor 50, thereby controlling the feedback energy absorbed by the resistor, as shown in fig. 3. Thus, resistor 50 is only activated after the storage capacitor has saturated, for consuming excess feedback braking energy.

In a second class of embodiments, the first current capture device 20 may be an energy consumer. Wherein the energy consumer may be a resistor 25 (as shown in fig. 4) or the like.

Specifically, when the dc bus voltage displayed by the voltmeter 11 is equal to or greater than the first preset voltage (i.e., there is a stall risk), the CPU 41 controls the duty ratio of the first high-frequency switch 31 to turn on the circuit in which the resistor 25 is located, so as to control the speed at which the feedback braking energy is consumed by the resistor 25, thereby controlling the feedback energy absorbed by the resistor, and further stabilizing the dc bus voltage to prevent it from exceeding the protection voltage. At this time, since the driver does not limit the strength of the feedback brake, the corresponding vehicle speed is slower and slower, thereby avoiding the risk of stall.

Of course, in another embodiment, the first current capturing device 20 may be configured as an energy accumulator and an energy consumer, and the respective switching devices of the energy accumulator and the energy consumer are controlled by a corresponding control strategy to conduct a corresponding circuit, so as to achieve effective capturing of the feedback current.

In an embodiment, the control system further comprises: a digital-to-analog converter 70 for converting the analog signal of the dc bus voltage detected by the voltage detection device 10 into a digital signal and outputting the digital signal of the converted dc bus voltage to the control device 40, as shown in fig. 2.

The overspeed control mode based on the direct current bus voltage can realize the downhill control of the vehicle. The control mode has a stall protection function, does not need to detect the speed of the vehicle and participate in speed control, and ensures that the driver can exert the braking capability of the motor to the maximum extent by stabilizing the voltage of the direct current bus, thereby preventing overspeed of the vehicle. Since the vehicle does not overspeed, it is less likely to stall. Therefore, during the operation of the overhead working truck, whether the battery is full, the limitation of a battery power Map (Map) or the direct current bus voltage of the driver caused by battery faults and the like is higher (or downhill stall), overspeed control based on the direct current bus voltage is inhibited from the source, and therefore the generation of the downhill stall risk is effectively prevented.

In summary, the invention creatively detects the direct current bus voltage of the driver through the voltage detection device; then capturing feedback current transmitted by the driver through a first current capturing device; and then, under the condition that the voltage of the direct current bus is equal to or greater than a first preset voltage, the control device controls the first switching device to conduct the first circuit so as to capture the feedback current by the first current capturing device. Therefore, the invention can intervene in the control strategy when the DC bus voltage exceeds a first preset voltage (for example, a certain voltage smaller than the protection voltage of the driver) (i.e. before the occurrence of downhill overspeed), and the DC bus voltage of the driver is reduced by capturing the feedback current, so that the brake moment is prevented from becoming smaller, and the occurrence of the risk of downhill stall is effectively restrained.

An embodiment of the present invention also provides an overhead working truck, which may include: the control system (namely the safety protection device) 1 is used for downhill working conditions.

The aerial work vehicle may further include: a parking brake 120; and a driver 2 for controlling the parking brake 120 to perform braking in case that the rotational speed of the motor is less than a preset rotational speed.

In an embodiment, the aerial vehicle may further comprise: battery 80, vehicle Control Unit (VCU) 90, motor 100, speed reducer 130, wheels 140, DC/DC converter 150, and the like, as shown in fig. 2. Wherein, the battery 80 is configured with a Battery Management System (BMS), and a Vehicle Control Unit (VCU) 90 performs information interaction with the BMS through a CAN bus. The VCU 90 may adjust the target rotation speed of the motor 100 according to the battery state and the fault information transmitted from the BMS.

Specifically, the control system for downhill operation captures the feedback current generated by the regenerative braking, and the motor 100 can achieve deceleration control of the wheels 140 through the speed reducer 130, so that the vehicle speed is lower and lower, since the driver 2 does not limit the intensity of the feedback braking. And, in case that the rotational speed of the motor 100 is less than the preset rotational speed, stopping is achieved by controlling the parking brake to perform braking. Therefore, when the driving system fails, the mode of firstly decelerating and then contracting brake can be adopted, so that the damage to the parking brake is reduced as much as possible, and the service life of the parking brake is prolonged.

The embodiment can absorb the energy generated by the feedback braking through the resistor/capacitor and timely control the speed reduction of the vehicle. When the feedback energy is insufficient, the energy storage capacitor is used for timely supplementing electricity so as to maintain the normal operation of the driver until the driver is completely stopped. Therefore, the parking brake can be prevented from being damaged by dynamic impact energy, the probability of high-speed band-type brake can be greatly reduced, the service life of the parking brake is prolonged, the risk of parking on a slope is reduced, and accordingly safer and more reliable downhill can be realized.

Specific details and benefits of the aerial vehicle provided by the embodiments of the present invention can be found in the above description of the feedback current control device, and are not repeated here.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.

In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition.

Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.

Claims

1. A control system for downhill conditions, the control system comprising:

the voltage detection device is used for detecting the direct current bus voltage of the driver;

the first current capturing device is used for capturing feedback current transmitted by the driver;

a first switching device for turning on a first circuit in which the first current capturing device is located; and

and the control device is used for controlling the first switching device to conduct the first circuit so as to capture the feedback current by the first current capturing device under the condition that the voltage of the direct current bus is equal to or greater than a first preset voltage.

2. The control system of claim 1, wherein the first preset voltage is less than a protection voltage of the driver.

3. The control system of claim 1, wherein the first current capture device is an energy store and/or an energy consumer.

4. A control system according to claim 3, wherein in the case where the first current capture device is the energy store, the control system further comprises:

a second current capture device; and

a second switching device for switching on a second circuit in which the second current capturing device is located,

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

6. The control system of claim 5, wherein the first high frequency switch and the second high frequency switch are field effect transistors.

7. The control system of claim 6, wherein the control means for turning on the first circuit by controlling the first switching means comprises: switching on the first circuit by controlling the duty cycle of the first high frequency switch to control the speed at which the feedback current is captured by the first current capture device, and

the control means for turning on the second circuit by controlling the second switching means includes: the second circuit is turned on by controlling the duty cycle of the second high frequency switch to control the speed at which the feedback current is captured by the second current capture device.

8. The control system of claim 4, wherein the second current capture device is an energy store and/or an energy consumer.

9. An aerial work vehicle, the aerial work vehicle comprising: a control system for downhill conditions according to any of claims 1-8.

10. The aerial vehicle of claim 9, wherein the aerial vehicle further comprises:

a parking brake; and

and the driver is used for controlling the parking brake to brake under the condition that the rotating speed of the motor is smaller than the preset rotating speed.