An emergency supplementary braking system and method for a pure electric wide-body dump truck

Abstract

An emergency supplementary braking system and method for a pure electric wide-body dump truck, including a main circuit and a control circuit. The main circuit includes a power supply system, a motor controller, and a permanent magnet synchronous traction motor. The power supply system drives the permanent magnet synchronous traction motor through the motor controller. The main circuit also includes braking resistors R1, R2, and R3 provided between the motor controller and the three-phase connection of the permanent magnet synchronous traction motor. It solves the problem of insufficient mechanical braking force, improves the emergency braking ability; reduces the energy loss caused by additional emergency braking during driving; improves the braking reliability and avoids the problem that the emergency braking function cannot be activated due to damage to the motor controller or power failure of the whole vehicle.

Description

Technical Field

[0001] The present invention relates to a dump truck, in particular to an emergency supplementary braking system and method for a pure electric wide-body dump truck. Background Art

[0002] With the country's strong promotion of the policy of green mines, more and more domestic mining industries are adopting pure electric wide-body dump trucks. There are two sets of driving braking systems for pure electric wide-body dump trucks: one is a commonly used electric braking system for deceleration and slowdown, which converts mechanical energy into electrical energy through a traction motor and rectifies and feeds it back to the power supply system through a motor controller; the other is a basic mechanical braking system that uses air as the power source. To meet the domestic transportation needs, the tonnage of pure electric wide-body dump trucks has gradually increased, from a load capacity of 60 tons to a load capacity of 70 to 75 tons, and the motor power has also increased accordingly. However, the basic mechanical braking system of the rear axle has not changed. In this way, there is no problem under normal operation, but when the vehicle is fully loaded and going downhill, in the case of insufficient or ineffective electric braking, braking with the basic brake may not be able to stop the vehicle, resulting in vehicle out of control, and in severe cases, vehicle rollover or casualties may occur.

[0003] To avoid the above situation and improve braking safety, two common methods are adopted for existing pure electric wide-body dump trucks: one is to add an eddy current retarder between the output shafts of the middle bridge and the rear bridge, which is powered by adding a set of independent storage batteries (24V) and can provide a maximum braking torque of 3300 N·m; the other is to connect a set of braking resistors in parallel between the power supply system and the motor controller. When the power supply system is fully charged or faulty, the braking resistor compensates for the consumed and fed-back electrical energy.

[0004] For the first existing technical solution, connecting the front and rear drive shafts through two couplings will cause at least 4% of energy transmission loss during vehicle operation, reducing the product's use economy. In addition, an additional storage battery needs to be added as the excitation power source for the retarder, and the storage battery needs to be regularly inspected and maintained to ensure the product's reliability under emergency use. For the second existing technical solution, it can only be used as a compensation when there are fewer power batteries or the electrical energy cannot be absorbed. When the motor controller is damaged or the whole vehicle is powered off, it cannot work to generate electric braking force. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an emergency supplementary braking system and method for a pure electric wide-body dump truck, which can supplement the problem of insufficient mechanical braking force, improve the emergency braking ability; reduce the energy loss caused by additional emergency braking during driving; improve braking reliability and avoid the problem that the emergency braking function cannot be put into use due to damage to the motor controller or power-off of the whole vehicle.

[0006] To solve the above technical problems, the technical solution of the present invention is: an emergency supplementary braking system for a pure electric wide-body dump truck, including a main circuit and a control circuit. The main circuit includes a power supply system, a motor controller, and a permanent magnet synchronous traction motor. The power supply system drives the permanent magnet synchronous traction motor through the motor controller. The main circuit also includes braking resistors R1, R2, and R3 provided between the three-phase connection of the motor controller and the permanent magnet synchronous traction motor. The control circuit includes a vehicle controller VCU, a three-wire contactor K1, redundant relays KM1 and KM2, and a battery. One ends of the braking resistors R1, R2, and R3 are connected to each other, and the other ends of the braking resistors R1, R2, and R3 are respectively connected to the three-phase connection through the normally open contacts of the three-wire contactor K1. The coil of the three-wire contactor K1, the battery, and the coil of the relay KM1 are connected in parallel. The branch where the coil of the three-wire contactor K1 is located is provided with the normally open contacts of the relays KM1 and KM2. The branch where the coil of the relay KM1 is located is provided with a cab operation switch S1. The control port 1 of the vehicle controller VCU is connected to the coil of the relay KM1.

[0007] As an improvement, the battery outputs 24V direct current.

[0008] As an improvement, the control port 1 of the vehicle controller VCU outputs a high level.

[0009] As an improvement, the maximum braking power is 275kW, the resistance value of the braking resistor is 0.75Ω, the maximum power of a single permanent magnet synchronous traction motor is 139kW, and the maximum power of two permanent magnet synchronous traction motors is 278kW.

[0010] The control method of the present invention includes the following steps:

[0011] (1) When the current SOC value of the battery of the power supply system is too high to fully absorb the electric braking energy, start consuming the braking resistor to compensate for the current electric braking force;

[0012] (2) When there is a fault in the main circuit equipment or line or the vehicle is completely powered off, the permanent magnet synchronous traction motor uses the rotation of the rotor permanent magnet to generate an induced electromotive force in the stator winding, forms an induced current through the braking resistor circuit, and thus forms an induced magnetic field, which generates a resistance torque on the rotor, thereby generating an electric braking force. The magnitude of the resistance torque is related to the speed. The higher the vehicle speed, the higher the motor speed at this time, the greater the generated resistance torque, and the better the compensation for the vehicle's emergency braking force; when the vehicle speed decreases and the motor speed decreases, the vehicle is in a controllable and safe state, and the generated resistance torque will also decrease, adapting to the vehicle's demand for emergency braking supplementary force.

[0013] As an improvement, there are specifically two control methods:

[0014] (1) When the vehicle control unit (VCU) functions properly and detects that the main circuit is abnormal and the electric braking energy cannot be fed back to the power supply system, the VCU outputs a high level through control port 1 to energize the coils of relays KM1 and KM2, causing the normally open contacts of relays KM1 and KM2 to close. The coil of three-phase contactor K1 is energized, and the normally open contact of three-phase contactor K1 closes, and braking resistors R1, R2, and R3 are put into operation.

[0015] (2) When the VCU is unable to send commands, the driver operates the cab operation switch S1 to supply power to the coils of relays KM1 and KM2 through a hardwired method, causing the normally open contacts of relays KM1 and KM2 to close. The coil of three-phase contactor K1 is energized, and the normally open contact of three-phase contactor K1 closes, and braking resistors R1, R2, and R3 are put into operation.

[0016] The beneficial effects brought by the present invention compared with the prior art are as follows:

[0017] 1. Complement the problem of insufficient mechanical braking force and improve the emergency braking ability;

[0018] 2. Reduce the energy loss caused by additional emergency braking during driving;

[0019] 3. Improve the braking reliability and avoid the problem that the emergency braking function cannot be put into operation due to the damage of the motor controller or the power-off of the whole vehicle. Description of the Drawings

[0020] Figure 1 is the main circuit diagram.

[0021] Figure 2 is the control circuit diagram.

[0022] Figure 3 is the motor parameter model setting diagram.

[0023] Figure 4 is the system simulation model diagram.

[0024] Figure 5 is the simulation motor shaft end power curve diagram under the state of the traction motor speed of 2000 r / min.

[0025] Figure 6 is the simulation motor shaft end torque curve diagram under the state of the traction motor speed of 2000 r / min.

[0026] Figure 7 is the simulation motor shaft power curve diagram at different speeds under the state of the traction motor speed of 1200 - 2000 r / min.

[0027] Figure 8 is the braking torque and power provided by the eddy current. Detailed implementation mode

[0028] The present invention will be further described below in conjunction with the accompanying drawings of the specification.

[0029] An emergency supplementary braking system for a pure electric wide-body dump truck includes a main circuit and a control circuit. As Figure 1 shown, the main circuit includes a power supply system, a motor controller, and a permanent magnet synchronous traction motor. The power supply system drives the permanent magnet synchronous traction motor through the motor controller. The main circuit further includes braking resistors R1, R2, and R3 provided between the three-phase wiring of the motor controller and the permanent magnet synchronous traction motor. As Figure 2 shown, the control circuit includes a vehicle controller VCU, a three-wire contactor K1, mutually redundant relays KM1 and KM2, and a storage battery. One ends of the braking resistors R1, R2, and R3 are connected to each other. The other ends of the braking resistors R1, R2, and R3 are respectively connected to the three-phase wiring through the normally open contacts (1,2; 3,4; 5,6) of the three-wire contactor K1. The coil of the three-wire contactor K1, the storage battery, and the coil of the relay KM1 are connected in parallel. The branch where the coil of the three-wire contactor K1 is located is provided with the normally open contacts (1,2; 3,4) of the relays KM1 and KM2. The branch where the coil of the relay KM1 is located is provided with a cab operation switch S1. The control port 1 of the vehicle controller VCU is connected to the coil of the relay KM1. The control port 2 of the vehicle controller VCU is connected to the storage battery through the normally open contact (13,14) of the three-wire contactor K1.

[0030] The braking control method of the present invention includes the following steps:

[0031] (1) When the current SOC value of the battery of the power supply system is too high to fully absorb the electric braking energy, start the consumption of the braking resistor to compensate for the current electric braking force;

[0032] (2) When a main circuit device or line fails or the whole vehicle loses power, the permanent magnet synchronous traction motor uses the rotation of the rotor permanent magnet to generate an induced electromotive force in the stator winding, forms an induced current through the braking resistor circuit, thereby forms an induced magnetic field, generates a resistance torque on the rotor, and thus generates an electric braking force. The magnitude of the resistance torque is related to the rotational speed. The higher the vehicle speed, the higher the motor speed at this time, the greater the generated resistance torque, and the better the compensation for the emergency braking force of the vehicle; when the vehicle speed decreases and the motor speed decreases, the vehicle is in a controllable and safe state, and the generated resistance torque will also decrease, adapting to the vehicle's demand for emergency braking supplementary force.

[0033] The control strategy of the present invention: K1 is the three-phase contactor of the braking main circuit; KM1 and KM2 are the control circuit relays, with a mutually redundant design; S1 is the driver's manual operation switch; the storage battery provides a 24V emergency power supply for the whole vehicle.

[0034] Two specific control methods:

[0035] (1) When the vehicle control unit (VCU) functions properly and detects that the main circuit is abnormal and the electric braking energy cannot be fed back to the power supply system, the VCU outputs a high level through port 1 to control the relay coils of relays KM1 and KM2 to be energized, so that the normally open contacts (1, 2; 3, 4) of KM1 and KM2 are closed, the coil of three-phase contactor K1 is energized, and the normally open contacts (1, 2; 3, 4; 5, 6) of three-phase contactor K1 are closed, and braking resistors R1, R2, and R3 are put into operation;

[0036] (2) When the VCU cannot send commands (such as when the vehicle is powered off), the driver can operate the manual switch S1 to supply power to the relay coils of relays KM1 and KM2 through a hardwired method, so that the normally open contacts (1, 2; 3, 4) of relays KM1 and KM2 are closed, the coil of three-phase contactor K1 is energized, and the normally open contacts (1, 2; 3, 4; 5, 6) of three-phase contactor K1 are closed, and braking resistors R1, R2, and R3 are put into operation.

[0037] Simulation description: Based on the Amesim software, the parameters of the traction motor in the green control electric drive system equipped with the HC105E pure electric wide-body dump truck are used for simulation calculation to obtain the required parameters of the equipped braking resistors.

[0038] I. Motor parameter model: The motor is a permanent magnet synchronous motor with a rated power of 220 kW. As Figure 3 shown, the basic parameters of the motor required for building the model: direct-axis inductance, quadrature-axis inductance, stator phase resistance, magnetic flux, number of pole pairs, initial angle, etc.

[0039] II. As Figure 4 shown, build the system model.

[0040] III. Operating parameter settings: The vehicle driving speed does not exceed 30 km / h. Emergency supplementary braking is mainly used for the vehicle's heavy-load downhill condition. When electric braking is insufficient or fails, the basic braking must be used to stop the vehicle. As a way of supplementary braking, emergency braking should provide reliable braking torque or braking power within the full speed range in an ideal state. There are two situations: one is that the transmission control is normal and the gear reduction operation can be performed according to the vehicle speed. At this time, the rotational speed of the traction motor is maintained at about 2000 r / min; the other is that the transmission is abnormally stuck in a certain fixed gear, and the motor speed decreases as the vehicle speed decreases; when the vehicle speed is 15 km / h, it is assumed that the transmission is stuck in the 5th gear. At this time, the motor speed is the lowest, which is 1200 r / min. This simulation calculation studies that when the vehicle speed is higher than 15 km / h, the emergency supplementary braking force should be effective enough.

[0041] Study the magnitude of the electric braking power when the resistance value of the braking resistor is different. The single-phase resistance values are selected as 0.5Ω, 0.75Ω, 1Ω, and 1.25Ω.

[0042] IV. Simulation Results:

[0043] As Figure 5 , 6 shown, the simulation results under the condition that the traction motor speed is 2000 r / min:

[0044] When R = 1.25Ω, the stable power at the motor shaft end: -112 kW, torque: 533 N·m;

[0045] When R = 1Ω, the stable power at the motor shaft end: -128 kW, torque: 610 N·m;

[0046] When R = 0.75Ω, the stable power at the motor shaft end: -139 kW, torque: 664 N·m;

[0047] When R = 0.5Ω, the stable power at the motor shaft end: -132 kW, torque: 632 N·m.

[0048] As Figure 7 shown, the simulation results under the condition that the traction motor speed is 1200 - 2000 r / min: Study the variation of the shaft power with the speed of the traction motor at different speeds.

[0049] Data Comparison and Conclusion: As Figure 8 shown, the braking torque and power provided by the eddy current, calculated proportionally, the maximum braking power currently installed on the 105 pure electric wide-body dump truck is 275 kW. The above is the simulation analysis based on the parameters of the Green Control dual-motor power system. Select the braking resistor value of 0.75Ω, the maximum power of a single motor is 139 kW, and the dual-motor is 278 kW, meeting the demand for replacing the eddy current power. Under different vehicle speeds, the braking powers of the two methods basically show a linear change. The slope of this scheme is smaller and it is relatively better.

Claims

1. An emergency supplementary braking system for a pure electric wide-body dump truck, comprising a main circuit and a control circuit. The main circuit includes a power supply system, a motor controller, and a permanent magnet synchronous traction motor. The power supply system drives the permanent magnet synchronous traction motor through the motor controller, and is characterized in that: The main circuit further includes braking resistors R1, R2, and R3 provided between the motor controller and the three-phase connection of the permanent magnet synchronous traction motor; the control circuit includes a vehicle controller VCU, a three-wire contactor K1, redundant relays KM1 and KM2, and a storage battery. One ends of the braking resistors R1, R2, and R3 are connected to each other. The other ends of the braking resistors R1, R2, and R3 are respectively connected to the three-phase connection through the normally open contacts of the three-wire contactor K1. The coil of the three-wire contactor K1, the storage battery, and the coil of the relay KM1 are connected in parallel. The branch where the coil of the three-wire contactor K1 is located is provided with the normally open contacts of the relays KM1 and KM2. The branch where the coil of the relay KM1 is located is provided with a cab operation switch S1. The control port 1 of the vehicle controller VCU is connected to the coil of the relay KM1; (1) When the current SOC value of the power supply system battery is too high to fully absorb the electric braking energy, the braking resistors are started to consume and compensate for the current electric braking force; (2) When there is a fault in the main circuit equipment or line or the whole vehicle is powered off, the permanent magnet synchronous traction motor uses the rotation of the rotor permanent magnet to generate an induced electromotive force in the stator winding, and forms an induced current through the braking resistor circuit, thereby forming an induced magnetic field, generating a resistance torque on the rotor, and generating an electric braking force; (3) When the vehicle controller VCU functions normally and detects that the main circuit is abnormal and the electric braking energy cannot be fed back to the power supply system, the vehicle controller VCU outputs a high level through the control port 1 to control the coils of the relays KM1 and KM2 to be energized, so that the normally open contacts of the relays KM1 and KM2 are closed, the coil of the three-phase contactor K1 is energized, the normally open contacts of the three-phase contactor K1 are closed, and the braking resistors R1, R2, and R3 are put into operation; (4) When the vehicle controller VCU cannot send an instruction, the driver operates the cab operation switch S1 to supply power to the coils of the relays KM1 and KM2 in a hard-wired manner, so that the normally open contacts of the relays KM1 and KM2 are closed, the coil of the three-phase contactor K1 is energized, the normally open contacts of the three-phase contactor K1 are closed, and the braking resistors R1, R2, and R3 are put into operation.

2. The emergency supplementary braking system for a pure electric wide-body dump truck according to claim 1, wherein: The storage battery outputs 24V DC power.

3. The emergency supplementary braking system for a pure electric wide-body dump truck according to claim 1, wherein: The control port 1 of the vehicle controller VCU outputs a high level.

4. The emergency supplementary braking system for a pure electric wide-body dump truck according to claim 1, wherein: The maximum braking power is 275kW, the resistance value of the braking resistor is 0.75Ω, the maximum power of a single permanent magnet synchronous traction motor is 139kW, and the maximum power of two permanent magnet synchronous traction motors is 278kW.

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