Motor active speed reduction and safe shutdown method for EPS controller

Abstract

The present application relates to the technical field of electric power steering system, in particular to a motor active speed reduction and safe shutdown method for EPS controller. Compared with the prior art, the present application adds system strategy, so that the motor active speed reduction and safe shutdown are realized without changing the existing circuit structure, and the MOSFET is prevented from being damaged by breakdown. The present application reduces the cost of safe shutdown and simplifies the process.

Description

Technical Field

[0001] This invention relates to the field of electric power steering system technology, specifically a method for active motor deceleration and safety shutdown in an EPS controller. Background Technology

[0002] When the electric power steering system controller detects a fault, it needs to shut down the controller and disconnect the MOSFET. If the electric power steering motor is rotating at high speed at this time, it will release energy, generate current, and create a back electromotive force.

[0003] When the reverse electromotive force voltage exceeds the maximum rated withstand voltage of the MOSFET, the MOSFET will enter avalanche mode. At this time, if the energy released by the motor coil is greater than the avalanche energy that the MOSFET can withstand, the MOSFET will be damaged by breakdown.

[0004] Currently, the above problems are mainly solved by optimizing the circuit or optimizing the motor characteristics. However, optimizing the circuit has the disadvantage of complex circuit structure, and optimizing the motor characteristics has the disadvantage of high cost and complex process.

[0005] Therefore, it is necessary to design a method for active motor deceleration and safe shutdown for EPS controllers to achieve safe shutdown without changing the existing circuit structure. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for active motor deceleration and safe shutdown for EPS controllers, which achieves safe shutdown without changing the existing circuit structure.

[0007] To achieve the above objectives, the present invention provides a method for active motor deceleration and safety shutdown in an EPS controller, comprising the following steps: Step 1, the microprocessor (MCU) detects whether a system fault has occurred; if a fault occurs, proceed to Step 2; Step 2, the motor position sensor (RPS) sends the detected motor speed to the MCU in real time; the MCU compares the obtained motor speed with a preset speed threshold 1 and / or speed threshold 2; if the motor speed ≥ speed threshold 1, proceed to Step 3; if the motor speed < speed threshold 1 and the motor speed ≥ speed threshold 2, proceed to Step 5; Step 3, the controller enters ASC mode, the MCU sends a control command to the pre-drive chip, the pre-drive chip controls the three upper-bridge MOSFETs of the three-phase bridge to disconnect and the three lower-bridge MOSFETs to turn on, and the motor actively decelerates; Step 4, waits for the motor speed to decrease, and the MCU... The obtained motor speed is compared with the preset speed threshold 2. If the motor speed is less than the speed threshold 2, the controller exits ASC mode, and the microprocessor MCU sends a control command to the pre-drive chip. The pre-drive chip controls the three-phase bridge MOSFETs to resume normal conduction and shutdown modes, and the motor resumes normal rotation. Step 5: The microprocessor MCU sends a control command to the pre-drive chip, and the pre-drive chip controls all three-phase bridge MOSFETs to disconnect. Step 6: After waiting for a time not less than the freewheeling time, the microprocessor MCU compares the obtained motor speed with the preset speed threshold 3. If the motor speed is greater than the speed threshold 3, the freewheeling continues until the motor speed equals the speed threshold 3, and then proceeds to step 7. If the motor speed is less than or equal to the speed threshold 3, then proceeds to step 7. Step 7: The microprocessor MCU sends a control command to the phase separation driver chip, and the phase separation driver chip controls the three-phase phase separation MOSFETs to disconnect.

[0008] The control signal output terminal 1 of the microprocessor MCU is connected to the control signal input terminal of the pre-driver chip. The control signal output terminal 1 of the pre-driver chip is connected to the gates of the three MOSFETs on the upper bridge of the three-phase bridge. The control signal output terminal 2 of the pre-driver chip is connected to the gates of the three MOSFETs on the lower bridge of the three-phase bridge. The sources of the three MOSFETs on the upper bridge of the three-phase bridge are connected to the drains of the three MOSFETs on the lower bridge of the three-phase bridge in sequence. The drains of the three MOSFETs on the lower bridge of the three-phase bridge are connected to the drains of the three phase-separated MOSFETs in sequence. The gates of the three phase-separated MOSFETs are connected to the control signal output terminal of the phase-separated driver chip. The control signal input terminal of the phase-separated driver chip is connected to the control signal output terminal 2 of the microprocessor MCU. The sources of the three phase-separated MOSFETs are connected to the three phase lines of the motor. A motor position sensor RPS is installed on the motor. The motor speed signal output terminal of the motor position sensor RPS is connected to the motor speed signal input terminal of the microprocessor MCU.

[0009] The drains of the three MOSFETs on the upper bridge of the three-phase bridge are connected to the positive terminal of the battery, and the negative terminal of the battery is grounded.

[0010] The sources of the three MOSFETs in the lower bridge of the three-phase bridge are connected to three sampling resistors and then grounded.

[0011] The speed threshold is 5500 RPM to 6000 RPM.

[0012] The second speed threshold is 4800 RPM to 5300 RPM.

[0013] The speed threshold three is 2500RPM~4000RPM.

[0014] The duration of the continuous stream is 10ms to 100ms.

[0015] Compared with existing technologies, this invention adds a system strategy, thereby achieving active motor deceleration and safe shutdown without changing the existing circuit structure, preventing MOSFET damage. This invention reduces the cost of safe shutdown and simplifies the process. Attached Figure Description

[0016] Figure 1 This is a circuit diagram of the present invention.

[0017] Figure 2 This is a schematic diagram of the follow-through process of the energy generated by the rotation of the motor in this invention.

[0018] Figure 3 This is a flowchart of the present invention. Implementation

[0019] The present invention will now be further described with reference to the accompanying drawings.

[0020] like Figure 3 As shown, this invention is a method for active motor deceleration and safety shutdown in an EPS controller, comprising the following steps:

[0021] Step 1: The microprocessor (MCU) detects whether the system has malfunctioned. If a malfunction occurs, proceed to Step 2.

[0022] Step 2: The motor position sensor RPS sends the detected motor speed to the microprocessor MCU in real time. The microprocessor MCU compares the obtained motor speed with the preset speed threshold 1 and / or speed threshold 2. If the motor speed is ≥ speed threshold 1, proceed to step 3. If the motor speed is < speed threshold 1 and the motor speed is ≥ speed threshold 2, proceed to step 5.

[0023] Step 3: The controller enters ASC mode. The microprocessor (MCU) sends control commands to the pre-driver chip. The pre-driver chip controls the three upper-bridge MOSFETs of the three-phase bridge to turn off and the three lower-bridge MOSFETs to turn on. By using the short circuit between the phase lines, the motor can actively reduce its speed, thus avoiding excessive motor speed and the generation of excessive energy, which could cause the MOSFETs to break down when they are turned off.

[0024] Step 4: Wait for the motor speed to decrease. The microprocessor MCU will compare the obtained motor speed with the preset speed threshold 2. If the motor speed is less than the speed threshold 2, it means that the motor has completed the active speed reduction. The controller will then exit ASC mode and the microprocessor MCU will send a control command to the pre-drive chip. The pre-drive chip will control the three-phase bridge MOSFETs to resume normal conduction and shutdown modes, and the motor will resume normal rotation.

[0025] Step 5: The microprocessor (MCU) sends a control command to the pre-driver chip, which then controls all MOSFETs of the three-phase bridge to disconnect.

[0026] Step 6: After waiting for a period not less than the freewheeling time, the microprocessor (MCU) compares the obtained motor speed with a preset speed threshold three. If the motor speed > speed threshold three, the freewheeling continues until the motor speed equals speed threshold three, then proceed to step 7. If the motor speed ≤ speed threshold three, then proceed to step 7. If the motor speed ≤ speed threshold three, and after a period of time... Figure 2 In the freewheeling process shown, the energy generated by the motor rotation is lower than the avalanche energy of the MOSFET. At this point, the energy is insufficient to break down and damage the MOSFET.

[0027] Step 7: The microprocessor (MCU) sends a control command to the phase separation driver chip, which then controls the three-phase phase separation MOSFETs to disconnect.

[0028] like Figure 1As shown, the control signal output terminal 1 of the microprocessor (MCU) is connected to the control signal input terminal of the pre-driver chip. The control signal output terminal 1 of the pre-driver chip is connected to the gates of the three MOSFETs on the upper bridge of the three-phase bridge. The control signal output terminal 2 of the pre-driver chip is connected to the gates of the three MOSFETs on the lower bridge of the three-phase bridge. The sources of the three MOSFETs on the upper bridge are sequentially connected to the drains of the three MOSFETs on the lower bridge. The drains of the three MOSFETs on the lower bridge are sequentially connected to the drains of the three phase-separated MOSFETs. The gates of the phase-separated MOSFETs are connected to the control signal output terminal of the phase-separation driver chip. The control signal input terminal of the phase-separation driver chip is connected to the control signal output terminal 2 of the microprocessor (MCU). The sources of the phase-separated MOSFETs are connected to the three phase lines of the motor. A motor position sensor (RPS) is installed on the motor. The motor speed signal output terminal of the RPS is connected to the motor speed signal input terminal of the microprocessor (MCU). The drains of the three MOSFETs on the upper bridge are connected to the positive terminal of the battery, and the negative terminal of the battery is grounded. The sources of the three MOSFETs on the lower bridge are connected to three sampling resistors and then grounded.

[0029] Preferably, the first speed threshold is 5500 RPM to 6000 RPM. The second speed threshold is 4800 RPM to 5300 RPM. The third speed threshold is 2500 RPM to 4000 RPM. The freewheeling duration is 10ms to 100ms. Example 1

[0030] In this example, the first speed threshold is 5500 RPM. The second speed threshold is 4800 RPM, and the third speed threshold is 4000 RPM. The freewheeling duration is 100 ms.

[0031] The microprocessor (MCU) detection system malfunctions. The motor position sensor (RPS) detects a motor speed of 5634 RPM and sends it to the MCU in real time. The MCU compares the obtained motor speed with a pre-set speed threshold. If the motor speed (5634 RPM) > 5500 RPM, the controller enters ASC mode. The MCU sends a control command to the pre-drive chip, which controls the three upper-bridge MOSFETs of the three-phase bridge to disconnect and the three lower-bridge MOSFETs to turn on, causing the motor to actively reduce speed. After the motor speed decreases, the MCU compares the obtained motor speed (4767 RPM) with a pre-set speed threshold. If the motor speed (4767 RPM) < 4800 RPM, the controller exits ASC mode. The MCU sends a control command to the pre-drive chip, which controls the three-phase bridge MOSFETs to return to their normal on / off state, and the motor resumes normal rotation. At this point, the fault still exists, and the motor speed is 4767 RPM < 4800 RPM. The microprocessor (MCU) sends a control command to the pre-drive chip, which controls all MOSFETs of the three-phase bridge to disconnect. After waiting for at least 100ms, the MCU compares the obtained motor speed of 3778 RPM with the preset speed threshold. The motor speed is 3778 RPM < 4000 RPM. The MCU then sends a control command to the phase separation drive chip, which controls the three-phase phase separation MOSFETs to disconnect. Example 2

[0032] In this example, the first speed threshold is 6000 RPM. The second speed threshold is 5300 RPM, and the third speed threshold is 4000 RPM. The freewheeling duration is 100 ms.

[0033] The microprocessor (MCU) detection system malfunctions. The motor position sensor (RPS) detects a motor speed of 5734 RPM and sends it to the MCU in real time. The MCU compares the obtained motor speed with two preset speed thresholds: 5734 RPM < 6000 RPM and 5734 RPM > 5300 RPM. The MCU then sends a control command to the pre-driver chip, which disconnects all MOSFETs in the three-phase bridge. After waiting for at least 100ms, the MCU compares the obtained motor speed of 3378 RPM with a third preset speed threshold: 3378 RPM < 4000 RPM. The MCU then sends a control command to the phase separation driver chip, which disconnects the three-phase phase separation MOSFETs.

[0034] This invention adds a system strategy, thereby achieving active motor deceleration and safe shutdown without changing the existing circuit structure, preventing MOSFET damage. This invention also reduces the cost of safe shutdown and simplifies the manufacturing process.

Claims

1. A method for active motor deceleration and safety shutdown in an EPS controller, characterized in that: Includes the following steps: Step 1: The microprocessor (MCU) detects whether the system has malfunctioned. If a malfunction occurs, proceed to Step 2. Step 2: The motor position sensor RPS sends the detected motor speed to the microprocessor MCU in real time. The microprocessor MCU compares the obtained motor speed with the preset speed threshold 1 and / or speed threshold 2. If the motor speed is ≥ speed threshold 1, then proceed to step 3. If the motor speed is < speed threshold 1 and the motor speed is ≥ speed threshold 2, then proceed to step 5. Step 3: The controller enters ASC mode, and the microprocessor (MCU) sends control commands to the pre-driver chip. The pre-driver chip controls the three upper bridge MOSFETs of the three-phase bridge to turn off and the three lower bridge MOSFETs to turn on, so that the motor actively slows down. Step 4: Wait for the motor speed to decrease. The microprocessor MCU will compare the obtained motor speed with the preset speed threshold 2. If the motor speed is less than the speed threshold 2, the controller will exit ASC mode. The microprocessor MCU will send a control command to the pre-drive chip. The pre-drive chip will control the three-phase bridge MOSFET to restore the normal conduction and cutoff modes, and the motor will resume normal rotation. Step 5: The microprocessor (MCU) sends a control command to the pre-driver chip, which then controls all MOSFETs of the three-phase bridge to disconnect. Step 6: After waiting for a time not less than the continuous current duration, the microprocessor MCU will compare the obtained motor speed with the preset speed threshold three. If the motor speed is greater than the speed threshold three, the continuous current will continue until the motor speed equals the speed threshold three, and then proceed to step 7. If the motor speed is less than or equal to the speed threshold three, then proceed to step 7. Step 7: The microprocessor (MCU) sends a control command to the phase separation driver chip, which then controls the three-phase phase separation MOSFETs to disconnect.

2. The method for active motor deceleration and safety shutdown in an EPS controller according to claim 1, characterized in that: The control signal output terminal 1 of the microprocessor MCU is connected to the control signal input terminal of the pre-driver chip. The control signal output terminal 1 of the pre-driver chip is connected to the gates of the three MOSFETs on the upper bridge of the three-phase bridge. The control signal output terminal 2 of the pre-driver chip is connected to the gates of the three MOSFETs on the lower bridge of the three-phase bridge. The sources of the three MOSFETs on the upper bridge of the three-phase bridge are connected to the drains of the three MOSFETs on the lower bridge of the three-phase bridge in sequence. The drains of the three MOSFETs on the lower bridge of the three-phase bridge are connected to the drains of the three phase-separated MOSFETs in sequence. The gates of the three phase-separated MOSFETs are connected to the control signal output terminal of the phase-separated driver chip. The control signal input terminal of the phase-separated driver chip is connected to the control signal output terminal 2 of the microprocessor MCU. The sources of the three phase-separated MOSFETs are connected to the three phase lines of the motor. A motor position sensor RPS is installed on the motor. The motor speed signal output terminal of the motor position sensor RPS is connected to the motor speed signal input terminal of the microprocessor MCU.

3. The method for active motor deceleration and safety shutdown in an EPS controller according to claim 1, characterized in that: The drains of the three MOSFETs on the upper bridge of the three-phase bridge are connected to the positive terminal of the battery, and the negative terminal of the battery is grounded.

4. The method for active motor deceleration and safety shutdown in an EPS controller according to claim 1, characterized in that: The sources of the three MOSFETs in the lower bridge of the three-phase bridge are connected to three sampling resistors and then grounded.

5. The method for active motor deceleration and safety shutdown in an EPS controller according to claim 1, characterized in that: The speed threshold is 5500 RPM to 6000 RPM.

6. The method for active motor deceleration and safety shutdown in an EPS controller according to claim 1, characterized in that: The second speed threshold is 4800 RPM to 5300 RPM.

7. The method for active motor deceleration and safety shutdown in an EPS controller according to claim 1, characterized in that: The speed threshold three is 2500RPM~4000RPM.

8. The method for active motor deceleration and safety shutdown in an EPS controller according to claim 1, characterized in that: The duration of the continuous stream is 10ms to 100ms.

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