CN102120424A - Controller and control method of eddy-current retarder of combined braking system - Google Patents

Abstract

The invention relates to a controller and a control method for an electric eddy current retarder of a combined braking system, relating to an automobile electric eddy current retarder. The controller is composed of a microcomputer, a high-power transistor drive circuit, a brake pedal position sensor, a current feedback circuit, and a combination switch of an eddy current retarder. After the brake pedal is stepped on, the controller turns off the graded gear control, and first calculates the real-time braking force of the car according to the PWM control signal of the eddy current retarder, the input of the brake pedal position sensor, and the change of the car speed pulse. Then calculate the slope of the car, and then query the proportion of the eddy current retarder that is pre-stored in the internal memory corresponding to the slope value to share the car's downhill braking force, and apply the corresponding duty to the eddy current retarder electromagnetic coil The specific PWM control signal is used to output a custom power torque, so that the eddy current retarder can fully exert its auxiliary braking function on different slopes when the eddy current retarder meets the normal working conditions, and at the same time reduce the driver's operating intensity.

Description

Combined braking system eddy current retarder controller and control method

technical field

The invention relates to an automotive electronic control product, which is suitable for the control of the eddy current retarder in the combined braking system composed of the main brake and the eddy current retarder in the transport vehicle.

Background technique

According to the requirements of regulations, large and medium-sized operating vehicles must be equipped with auxiliary braking devices to consume the braking load of the vehicle during small and medium braking, and reduce the thermal load and contact wear of the main braking device of the vehicle. At the same time, during the continuous braking process of the car down a long slope, the auxiliary braking device can participate in the braking effect to ensure the braking efficiency of the main braking device in the case of emergency braking. The eddy current retarder is a commonly used auxiliary braking device, but its braking power is relatively small. Therefore, a reasonable and full use of the braking effect of the eddy current retarder can ensure that the car can safely and quickly drive the road section that needs continuous braking. Improve the transport economy of cars.

Patent 20071002225.0 proposes "a joint controller and control method of the main brake and retarder of the automobile", the controller senses the degree of the driver's manipulation of the main brake of the car through the position change of the brake pedal, and judges whether the engine retarder is needed Participate in the work and be able to adjust the braking torque of the eddy current retarder accordingly. This control method is based on the driver's braking operation, firstly controls the braking torque of the eddy current retarder according to the set ratio, and then makes limited adjustments to the braking torque of the eddy current retarder according to the change of the vehicle speed. This control method can effectively reduce the driver's operation, but the disadvantage is that the main braking device of the car must bear a certain proportion of the braking load and continue to work.

Patent 200810020499.7 proposes "the combined controller and control method of the eddy current retarder and the main brake of the vehicle". In the above, the eddy current retarder and the main brake of the car jointly participate in the braking effect, and the braking torque of the eddy current retarder is in a fixed proportional relationship with the braking torque of the main brake of the car, and is made according to the driving speed of the car. A certain amount of adjustments. During the continuous braking process, the main brake of the car is involved in the work, and it is difficult to give full play to the auxiliary braking effect of the eddy current retarder.

Chinese patent ZL200810022546.1 provides a "split eddy current retarder controller", which provides eddy current retarder neutral mode, gear mode, constant speed mode and joint control mode, according to the driver's According to the operation results of various switches, the controller makes the eddy current retarder enter different working states. Among them, in the joint control mode, the eddy current retarder outputs the braking torque in a fixed proportion according to the degree of the driver's operation of the brake pedal. This kind of controller has changed the controller type in the traditional sense, which is beneficial to the space layout and the design of different models, but the operation is more troublesome, and the braking load is shared according to a fixed ratio, and the continuous working time of the main brake of the car will be longer. It is difficult to achieve the purpose of reducing the contact wear of the main brake and reducing the working temperature of the contact parts as much as possible.

Contents of the invention

The object of the present invention is to provide a controller and a control method of the eddy current retarder in the combined braking system composed of the eddy current retarder and the main brake of the automobile. The driver can choose to manually operate the retarder according to the environment of the automobile. The combination switch enables the controller to enter the graded control mode for the eddy current retarder, or depress the brake pedal, the controller closes the graded control mode, and automatically enters the joint control mode.

Among them, when the controller is in the joint control mode, according to the magnitude of the braking force of the eddy current retarder and the main brake of the vehicle, and the change of the driving speed of the vehicle, the controller first identifies the slope of the road on which the vehicle is located, and then determines the eddy current retardation according to the slope. The size of the braking load that the speed reducer needs to bear, controls the eddy current retarder to output the corresponding braking torque. When the slope of the car is zero, the eddy current retarder does not bear the braking load; when the slope of the car is less than the set value, the eddy current retarder bears all the braking load; If the slope of the road is greater than or equal to the set value, the eddy current retarder bears the corresponding proportional part of the braking load that satisfies the vehicle's constant speed downhill on the slope, and the proportion of the braking load on the smaller slope is larger. In the joint braking mode, the driver can freely manipulate the brake pedal to make the main brake of the car play a corresponding braking effect according to the needs, but when the braking effect of the main brake of the car is greater than the preset level, the controller determines that the car is in an emergency. In the braking state, the eddy current retarder is prohibited from functioning.

The object of the present invention can be achieved by the following controller:

The controller is composed of a microcomputer, a high-power transistor drive circuit, a current feedback circuit, an eddy current retarder combination switch, and a brake pedal position sensor. The microcomputer includes input/output ports, internal bus, microcomputer CPU, PWM control unit, two interrupt controllers, electrically erasable programmable memory, analog/digital converter, read-only memory, random access memory, counter, timing The high-power transistor drive circuit includes optocouplers, insulated gate bipolar transistors, and freewheeling diodes. The current feedback circuit includes sampling resistors, precision voltage sources, and operational amplifiers. The combination switch of the eddy current retarder can provide 1, 2, 3, There are four switch signals for the 4th gear. The brake pedal position sensor contains a reset switch and a linear potentiometer.

The four gear output signals of the eddy current retarder combination switch and the battery voltage signal S1 are connected to the input/output ports of the microcomputer. The reset switch of the brake pedal position sensor is connected to the interrupt controller No. 2 and the input/output port, while the output of the linear potentiometer is connected to the input pin of the analog-to-digital converter. The PWM control unit has four outputs, each of which is connected to the control terminal of the optocoupler, the output terminal of the optocoupler is connected to the gate of the insulated gate bipolar transistor, and the drain of the insulated gate bipolar transistor is connected to the negative pole of the freewheeling diode and the positive pole of the battery. The source of the insulated gate bipolar transistor is connected to the anode of the freewheeling diode and the coil of the eddy current retarder. There are four sets of coils in the eddy current retarder, all of which are connected to the negative pole of the battery through a sampling resistor. In the current feedback circuit, the output of the sampling resistor is connected to the negative terminal of the operational amplifier, the output of the precision voltage source is connected to the positive terminal of the operational amplifier, and the output of the operational amplifier is connected to the No. 1 interrupt controller. The vehicle speed signal from the instrument panel is connected to the input terminal of the counter of the microcomputer.

The advantage of the present invention is that the driver can freely choose the manual mode or the foot mode to control the eddy current retarder according to the running status of the car and the road conditions of the car, and the conversion of the two modes is in the normal operation process of the driver. It is automatically completed by the controller through the opening and closing state of the switch. When the eddy current retarder is in the joint control mode, it can change the proportion of the braking load that satisfies the vehicle's constant downhill speed according to the gradient of the road surface, and fully exert the auxiliary braking function as an auxiliary braking device to reduce the pressure of the main brake of the vehicle. heat load. At the same time, the driver can independently control the main brake of the car according to the situation to adjust the driving speed of the car.

Description of drawings

Fig. 1 is a structural block diagram of the eddy current retarder controller of the present invention.

Fig. 2 is the main flowchart of the control method of the eddy current retarder controller of the present invention.

Fig. 3 is a flow chart of the hierarchical control mode subroutine of the eddy current retarder controller of the present invention.

Fig. 4 is a flow chart of the external interrupt service 1 of the eddy current retarder controller of the present invention.

Fig. 5 is a flow chart of the external interrupt service 2 of the eddy current retarder controller of the present invention.

Fig. 6 is a flow chart of the joint control mode subroutine of the eddy current retarder controller of the present invention.

Fig. 7 is a flow chart of timing interrupt service of the eddy current retarder controller of the present invention.

Fig. 8 is the relationship between the braking load ratio and the road gradient of the eddy current retarder of the present invention.

Notes in the drawings: 1-Eddy current retarder combination switch 2-Input/output port 3-Internal bus 4-Microcomputer CPU5-Eddy current retarder controller 6-Microcomputer 7-PWM control unit 8-Optical Coupling 9-insulated gate bipolar transistor 10-freewheeling diode 11-eddy current retarder coil 12-sampling resistor 13-precision voltage source 14-operational amplifier 15-No.1 interrupt controller 16-electrically erasable programmable memory 17-No. 2 interrupt controller 18-analog/digital converter 19-read only memory 20-random memory 21-counter 22-brake pedal position sensor 23-timer

Detailed ways

Below in conjunction with Fig. 1 illustrate the combined control system eddy current retarder controller circuit structure of the present invention:

As shown in FIG. 1 , the eddy current retarder controller of the combined braking system is composed of a microcomputer 6 , a high-power transistor drive circuit, a current feedback circuit, a combination switch 1 of the eddy current retarder, and a brake pedal position sensor 22 . Wherein microcomputer 6 comprises input/output port 2, internal bus 3, microcomputer CPU4, PWM control unit 7, No. 1 interrupt controller 15, No. 2 interrupt controller 17, electrically erasable programmable memory 16, modulus/digital Converter 18, read-only memory 19, random access memory 20, counter 21, timer 23, high-power transistor drive circuit includes optocoupler 8, insulated gate bipolar transistor 9, freewheeling diode 10, current feedback circuit includes sampling resistor 12, Precision voltage source 13, operational amplifier 14, eddy current retarder combination switch 1 can provide switching signals of 1, 2, 3, 4 gears, a total of four gears, brake pedal position sensor 22 contains a reset switch and a linear Potentiometer.

In FIG. 1 , the output signals of the four gears of the combination switch 1 of the eddy current retarder and the battery voltage signal S1 are connected to the input/output port 2 of the microcomputer 6 . The reset switch of the brake pedal position sensor 22 is connected to the No. 2 interrupt controller 17 and the input/output port 2 , while the output of the linear potentiometer is connected to the input pin of the analog/digital converter 18 . The PWM control unit 7 has four outputs, each of which is connected to the control terminal of the optocoupler 8, the output terminal of the optocoupler 8 is connected to the gate of the insulated gate bipolar transistor 9, and the drain of the insulated gate bipolar transistor 9 is connected to the freewheeling diode 10 The negative pole and the positive pole of the battery, the source of the insulated gate bipolar transistor 9 are connected to the positive pole of the freewheeling diode 10 and the eddy current retarder coil 11 . There are four groups of eddy current retarder coils 11, all of which are connected to the battery negative pole through the sampling resistor 12. The output of the sampling resistor 12 in the current feedback circuit is connected to the negative terminal of the operational amplifier 14, the output of the precision voltage source is connected to the positive terminal of the operational amplifier 14, and the output of the operational amplifier 14 is connected to the No. 1 interrupt controller 15. The vehicle speed signal obtained from the instrument panel is connected to the input terminal of the counter 21 of the microcomputer 6 .

The input/output port 2 of the microcomputer 6 receives digital signals such as the gear position of the combination switch 1 of the eddy current retarder, the low voltage signal S1 of the battery, the reset switch in the brake pedal position sensor 22, etc., and sends them to the microcomputer through the internal bus 3. The computer CPU4 obtains the operation information of the driver and the voltage state of the storage battery after calculation, which is one of the basis for the controller to control the braking torque of the eddy current retarder.

The counter 21 of microcomputer 6, under the cooperation of timer 23, records the number of vehicle speed pulses in a certain period of time, and together with the counting result in the last time period, calculates the vehicle acceleration.

The No. 2 interrupt controller 17 of the microcomputer 6 monitors the signal change of the reset switch in the brake pedal position sensor 22 . When the driver depresses the brake pedal, the reset switch is turned on, the No. 2 interrupt controller senses the change of the level from the reset switch from high to low, and the microcomputer 6 turns the eddy current retarder into the joint control mode and prohibits the classification control mode.

The current feedback circuit inputs the voltage drop on the sampling resistor 12 and the reference voltage of the precision voltage source 13 into the operational amplifier 14 of the comparator, and the comparison result is connected to the No. 1 interrupt controller 15 . If the voltage drop on the sampling resistor 12 is higher than the reference voltage of the precision voltage source 13, the microcomputer 6 will generate an external interruption to cut off the PWM pulse control signal of the eddy current retarder.

The read-only memory 19 in the microcomputer 6 stores the program code of the present invention and the relationship between the braking load ratio of the eddy current retarder and the slope when the automobile is going downhill at a constant speed, and the electrically erasable programmable memory 16 is in the process of program operation Store some intermediate operation results.

The eddy current retarder controller of the combined braking system of the present invention sets two working modes for the eddy current retarder: one is the hierarchical control mode, and the controller selects 1 of the combined switch 1 of the eddy current retarder according to the driver. , 2, 3, 4 gears, the PWM control of the corresponding duty ratio is carried out to the eddy current retarder; the second is the joint control mode, the controller makes the reset switch in the brake pedal position sensor 22 when the driver depresses the brake pedal After opening, the eddy current retarder works with the main brake of the car, and its braking torque is consistent with the braking load that the eddy current retarder should bear when the car goes downhill at a constant speed.

After the combined braking system eddy current retarder controller of the present invention is installed on the automobile, the driver only needs to select the gear of the eddy current retarder or step on the brake pedal when braking is required. The controller controls the braking torque of the eddy current retarder according to the pre-programmed program according to the working environment of the car.

The control method of the eddy current retarder of the combined braking system of the present invention is realized by executing the following program.

As shown in Figure 2, the eddy current retarder controller of the combined braking system executes the following main program after it is powered on.

(1) Combined brake system eddy current retarder controller 5 starts to execute the main program from step 200 .

(2) Then enter step 201 to allocate the input/output port of the microcomputer, and set its input or output state according to the resource configuration needs.

(3) Go to step 202 to initialize the timer and counter.

(4) Go to step 203 to initialize the interrupt controller.

(5) Go to step 204 to initialize the PWM control unit.

(6) Go to step 205 to clear the EEPROM space, which is used to save the intermediate calculation results.

(7) When the main program executes to step 206, it is a loop entry. First judge whether the control current of the electromagnetic coil of the eddy current retarder is too large. If the current is too large, jump to step 212 to handle the abnormal situation; otherwise, perform the next step in sequence.

(8) At step 207, the microcomputer extracts the input port information.

(9) In step 208, the microcomputer processes the input port information, calculates the gear code for the driver's operation on the combination switch of the eddy current retarder, and saves it in the EEPROM.

(10) Step 209 determines whether the calculated gear code has changed. If not, it means that the driver has not changed the operation of the combination switch of the eddy current retarder, and the program jumps back to step 206 at the loop entrance; otherwise, the next step is performed in sequence.

(11) Step 210 judges the battery voltage situation, if the battery voltage is too low, the program jumps to step 212 for abnormal situation processing; otherwise the program enters step 211 in order to call the hierarchical control mode of the eddy current retarder controller subroutine. After calling the subroutine, the program jumps to step 206 at the loop entry to execute the next loop.

(12) In step 212, the abnormal situation is handled, specifically, the PWM control signal of the electromagnetic coil of the eddy current retarder is cleared, so that the braking torque output of the eddy current retarder is zero. Then enter step 213, clear the saved gear code. After the abnormal situation is handled, the program jumps to step 206 at the loop entry to execute the next loop.

As shown in Figure 3, the eddy current retarder controller of the combined braking system calls the subroutine of the hierarchical control mode:

(1) The subroutine is executed from step 300.

(2) Entering step 301, the controller judges the driver's operation on the combination switch of the eddy current retarder according to the gear code, and identifies the 1st, 2nd, 3rd, 4th gear or neutral gear.

(3) Entering step 302, the controller applies corresponding PWM control pulses to the electromagnetic coil of the eddy current retarder according to different gear operations, so that the eddy current retarder outputs a corresponding level of braking torque.

(4) Go to step 303, call the hierarchical control mode subroutine and return.

As shown in Figure 4, the eddy current retarder controller of the combined braking system executes the external interrupt service 1 program:

When the eddy current retarder controller executes the main program shown in Figure 2, if the signal from the current feedback circuit meets the interrupt condition, the controller enters the external interrupt service 1 program.

(1) The external interrupt service 1 program is executed from step 400.

(2) Enter step 401, the microcomputer closes the external interrupt 1.

(3) Entering step 402, the microcomputer clears the PWM control signal of the electromagnetic coil of the eddy current retarder, so that the braking torque output of the eddy current retarder is zero.

(4) Go to step 403, and the microcomputer sets the flag bit for the excessive current of the electromagnetic coil of the eddy current retarder.

(5) Go to step 404, and the microcomputer reopens the external interrupt 1.

(6) Enter step 405, the program returns from the external interrupt service 1, and continues to execute the main program.

As shown in Figure 5, the eddy current retarder controller of the combined braking system executes the external interrupt service 2 program:

When the eddy current retarder controller executes the main program shown in Figure 2, if the driver depresses the brake pedal, the reset switch in the brake pedal position sensor is turned off, the signal meets the interrupt condition, and the controller enters the external interrupt Service 2 program.

(1) The external interrupt service 2 program is executed from step 500.

(2) Enter step 501, the microcomputer closes the external interrupt 2.

(3) Entering step 502, the microcomputer clears the PWM control signal of the electromagnetic coil of the eddy current retarder, so that the braking torque output of the eddy current retarder is zero.

(4) At step 503, call the joint control mode subroutine.

(5) Execute to step 504 to judge whether the brake pedal is reset. If the brake pedal is not reset, it indicates that the combined braking mode is not over, and the program jumps to step 503 to continue; otherwise, the program proceeds to the next step in sequence.

(6) Go to step 505, the microcomputer opens external interrupt 2.

(7) Enter step 506, the program returns from the external interrupt service 2 program.

As shown in Figure 6, the eddy current retarder controller of the combined braking system calls the combined control mode subroutine:

(1) The joint control mode subroutine is executed from step 600 .

(2) Entering step 601, the microcomputer obtains the current duty ratio of the PWM control signal of the electromagnetic coil of the eddy current retarder.

(3) Entering step 602, the microcomputer calculates the braking force of the eddy current retarder at the corresponding duty cycle.

(4) Go to step 603, the microcomputer passes the analog/digital converter the degree to which the driver depresses the brake pedal.

(5) Enter step 604, and calculate the braking force of the main brake of the vehicle according to the result of the previous step.

(6) Judging at step 605, whether the braking force of the main brake of the vehicle is greater than the set value. If greater, the program jumps to step 609 for execution; otherwise, proceeds to the next step in sequence.

(7) Go to step 606, the microcomputer acquires the current acceleration value of the car from the internal RAM.

(8) Go to step 607, and calculate the slope value of the ramp where the car is located according to the mechanics principle.

(9) Judging at step 608, whether the slope of the car is zero. If so, the program executes step 609 , clearing the PWM control signal of the electromagnetic coil of the eddy current retarder, so that the braking torque output of the eddy current retarder is zero; otherwise, the program executes step 610 .

(10) Look at step 610 first. The microcomputer inquires the read-only memory, and finds out the proportion of the braking load that the eddy current retarder should bear when the corresponding automobile goes downhill at a constant speed according to the known gradient value.

(11) Go to step 611, calculate and output the duty ratio of the PWM control signal of the electromagnetic coil of the eddy current retarder, so that the eddy current retarder outputs the braking torque corresponding to the proportion of the braking load.

(12) Go to step 612. This step is also entered after step 609 is executed. This step saves the duty cycle of the PWM control signal of the electromagnetic coil of the eddy current retarder in the random access memory.

(13) Go to step 613, call the joint control mode subroutine and return.

As shown in Figure 7, the eddy current retarder controller of the combined braking system executes the timing interrupt service routine:

(1) The timer interrupt service routine is executed from step 700.

(2) Go to step 701 and turn off the timer interrupt.

(3) Go to step 702, the microcomputer acquires the counting result of the vehicle speed pulse signal from the counter.

(4) Go to step 703 to calculate the current speed of the car.

(5) Go to step 704 and get the vehicle speed of the previous stage.

(6) Go to step 705, calculate the acceleration of the car.

(7) Enter step 706, save the vehicle acceleration result in the RAM.

(8) Go to step 707, and save the speed of the car in the RAM.

(9) Go to step 708 and enable timer interrupt.

(10) Go to step 709 and return from the timer service routine interrupt.

Figure 8 shows the corresponding relationship between the proportion of braking load borne by the eddy current retarder and the slope of the vehicle when the vehicle is running at a constant speed.

Figure 8 shows that when the slope of the car is less than a certain value, the eddy current retarder bears the entire proportion of the braking load when the car goes downhill, and when it is greater than or equal to this value, the braking load borne by the eddy current retarder The proportion of varies with the slope of the road, and the proportion is larger when the slope is small.

Claims (7)

1. A combined braking system eddy current retarder controller is characterized in that: the controller is composed of a microcomputer (6), a high-power transistor drive circuit, a current feedback circuit, an eddy current retarder combination switch (1), The brake pedal position sensor (22) is composed. Wherein microcomputer (6) comprises input/output port (2), internal bus (3), microcomputer CPU (4), PWM control unit (7), No. 1 interrupt controller (15), No. 2 interrupt controller ( 17), electrically erasable programmable memory (16), analog/digital converter (18), read-only memory (19), random access memory (20), counter (21), timer (23), high-power transistor The driving circuit includes an optocoupler (8), an insulated gate bipolar transistor (9), and a freewheeling diode (10), and the current feedback circuit includes a sampling resistor (12), a precision voltage source (13), an operational amplifier (14), an eddy current The retarder combination switch (1) can provide switching signals of four gears in total, 1, 2, 3, and 4 gears, and the brake pedal position sensor (22) includes a reset switch and a linear potentiometer. The four gear output signals of the eddy current retarder combination switch (1) and the battery voltage signal S1 are connected to the input/output port (2) of the microcomputer (6); the reset switch of the brake pedal position sensor (22) is connected to to the No. 2 interrupt controller (17) and input/output port (2), while the output of the linear potentiometer is connected to the input pin of the analog/digital converter (18). The PWM control unit (7) has four outputs, each of which is connected to the control terminal of the optocoupler (8), the output terminal of the optocoupler (8) is connected to the gate of the insulated gate bipolar transistor (9), and the insulated gate bipolar transistor ( The drain of 9) is connected to the negative pole of the freewheeling diode (10) and the positive pole of the accumulator, and the source of the insulated gate bipolar transistor (9) is connected to the positive pole of the freewheeling diode (10) and the eddy current retarder coil (11); There are four groups of retarder coils (11), all of which are connected to the battery negative pole by sampling resistors (12). In the current feedback circuit, the output of the sampling resistor (12) is connected to the negative terminal of the operational amplifier (14), the output of the precision voltage source is connected to the positive terminal of the operational amplifier (14), and the output of the operational amplifier (14) is connected to the No. 1 interrupt controller (15 ); Get the input terminal of the counter (21) of the counter (21) that the automobile speed signal that gets from dashboard connects microcomputer (6). 2. A control method for an eddy current retarder of a combined braking system, characterized in that: the eddy current retarder controller (5) can make the eddy current retarder work in a hierarchical control mode and a combined control mode, and the combined When the control mode is executed, the hierarchical control mode is prohibited; the eddy current retarder controller (5) enters the joint control mode after the driver depresses the brake pedal to open the reset switch of the brake pedal position sensor (22), And close the hierarchical control mode; after the eddy current retarder enters the joint control mode, the eddy current retarder controller (5) distributes the proportion of the braking load borne by the eddy current retarder according to the gradient. 3. The control method of the combined braking system eddy current retarder according to claim 2, characterized in that: the graded control mode is that the eddy current retarder controller (5) is combined according to the driver's combination of the eddy current retarder The gear operation of the switch (1) outputs a corresponding control pulse with a determined duty ratio to the insulated gate bipolar transistor (9), so that the eddy current retarder outputs a certain braking torque. 4. The control method of the eddy current retarder of the combined braking system according to claim 2, characterized in that: the combined control mode is that the eddy current retarder controller (5) makes the brake when the driver steps on the brake pedal. After the reset switch of the moving pedal position sensor (22) is opened, the microcomputer (6) obtains the duty ratio of the eddy current retarder control signal through the PWM control unit, and the analog/digital converter (18) extracts the brake pedal position sensor The input of (22), counter (21) and timer (23) calculate the variation of automobile speed pulse, first calculate the size of automobile actual braking force, then calculate the slope that automobile is in, then inquire about pre-stored in internal read-only memory The eddy current retarder corresponding to the ramp value in (19) shares the proportion of the vehicle’s constant downhill braking force, and a PWM control signal with a corresponding duty ratio is applied to the eddy current retarder coil (11) to output a certain braking force Torque, so that the eddy current retarder can fully exert its auxiliary braking effect on different slopes when the eddy current retarder meets the normal working conditions. 5. The control method of the eddy current retarder of the combined braking system according to claim 4, characterized in that: after the eddy current retarder controller (5) enters the combined control mode, if the value of the ramp where the car is located is Zero, the eddy current retarder controller (5) controls the eddy current retarder not to provide braking force. 6. The control method of the eddy current retarder of the combined braking system according to claim 4, characterized in that: after the eddy current retarder controller (5) enters the combined control mode, if the ramp where the car is located is less than the set A certain value, the braking force required by the car is provided by the eddy current retarder. 7. The control method of the eddy current retarder of the combined braking system according to claim 4, characterized in that: after the eddy current retarder controller (5) enters the combined control mode, after the brake pedal position sensor (22 ) When the input value exceeds a certain value, the eddy current retarder will not provide braking force.

Images