CN112061232A

CN112061232A - Intelligent electric power-assisted steering system of commercial vehicle

Info

Publication number: CN112061232A
Application number: CN202011047489.XA
Authority: CN
Inventors: 蒋立伟; 吴勇; 檀生辉; 王东; 刘恒; 朱岳松; 伍旭东; 王凯; 吴二导; 孙鸿健; 陶振; 王铭; 胡珍珠; 姜敏; 何志维; 齐红青
Original assignee: Wuhu Research Institute of Xidian University
Current assignee: Wuhu Research Institute of Xidian University
Priority date: 2020-09-29
Filing date: 2020-09-29
Publication date: 2020-12-11

Abstract

The invention discloses an intelligent electric power-assisted steering system of a commercial vehicle, which relates to the field of automobile steering systems and comprises a novel steering engine, a high-rotating-speed high-power motor and a high-voltage motor controller, wherein the motor controller and the motor are integrally designed to be connected with a shell or different shells; space and weight are effectively reduced; the motor design uses the high-speed switched reluctance motor, has reduced the motor volume, improve the motor cooling performance, the motor controller hardware adopts the third generation semiconductor carborundum power device, reduce the switching loss promptly, reduced the volume and the quality of controller again, the high-pressure high rotational speed motor drive system direct drive steering engine that comprises motor and controller, compare simple structure with hydraulic power-assisted, efficient, saved sealing member such as oil blanket, oil circuit, hydro-cylinder, simplified the structure, saved space and weight.

Description

Intelligent electric power-assisted steering system of commercial vehicle

Technical Field

The invention relates to the field of automobile steering systems, in particular to an intelligent electric power-assisted steering system of a commercial vehicle.

Background

The steering system used by the commercial vehicle with 3.5 tons of new energy and more comprises a circulating ball type steering gear, a steering control mechanism, a steering control valve, a steering oil pump, a steering oil tank, a steering hydraulic oil circuit, an oil pump driving motor and controller system, a high-voltage lead and a connector thereof and the like.

Such a steering system mainly has the following problems: 1. the system is complex in structure, each part is separated, the whole vehicle occupies large arrangement space, the weight is heavy, and the key index of unit mass energy consumption (Ekg) of the new energy commercial vehicle is particularly influenced; 2. under the condition that no power assistance is needed when the whole vehicle is electrified at high pressure and at high speed, namely under the condition that no steering requirement exists, the oil pump also works all the time, the rotating speed of the oil pump cannot be adjusted according to the actual working condition, the energy consumption is increased, and the endurance mileage of the electric vehicle is influenced.

In order to realize the automatic control of the steering system, a set of steering wheel control system is added on the steering column of the existing steering system to replace and execute the automatic control of the steering system by a driver.

However, in addition to the above problems, the current set of systems also has the following problems: 1. the system is more complex and has functional redundancy; 2. the oil pump driving motor and controller system and the steering wheel control system cannot communicate to realize coordination control.

Disclosure of Invention

The invention aims to provide an intelligent electric power steering system of a commercial vehicle, which consists of a novel steering gear, a high-rotating-speed high-power motor and a high-voltage motor controller, a traditional hydraulic power assisting device is not needed, the power source of the steering gear directly comes from the motor, and the novel steering gear, the high-rotating-speed high-power motor and the high-voltage motor controller are designed in a highly integrated manner, so that the space and the weight are saved. The novel motor is developed to meet the requirement of a steering system on low speed and large torque; a motor control system is developed, so that a driver can accurately control the motor to work in real time according to actual steering requirements by the electric control system; the development motor control system can communicate with other electronic control systems and can execute torque or angle control commands.

An intelligent electric power-assisted steering system of a commercial vehicle comprises an input shaft, a torque and rotation angle sensor, a motor, a steering engine, an output rocker arm and a controller, wherein the input shaft is connected with a torsion bar in the steering engine, the other end of the torsion bar is arranged in a hollow cavity of a screw rod, the torque and rotation angle sensor is connected with the controller and used for detecting the deformation quantity of the torsion bar, the motor and the output rocker arm are connected outside the steering engine, the controller is connected with the motor, the front section of a motor output shaft of the motor is provided with a worm, the worm is meshed with the worm wheel, and the worm wheel is connected with the output rocker arm through a transmission mechanism;

the motor adopts a switched reluctance motor, the controller comprises a main control circuit and a three-phase asymmetric half-bridge power conversion circuit, the main control circuit comprises a torque and corner signal processing circuit, a bus current/voltage/phase current sampling circuit, a motor winding temperature signal processing circuit, a CAN communication circuit, a CPU and FPGA processor circuit, a motor position signal processing circuit, an overcurrent and overvoltage signal comparison circuit, a simulation chopper circuit, a high-end driving and diagnosis circuit and a SiC logic driving protection circuit, and the three-phase asymmetric half-bridge power conversion circuit is formed by coupling a three-phase left half-bridge, a three-phase right half-bridge, a filter capacitor C, an anode contactor S, a pre-charging contactor S and a pre-charging resistor R.

Preferably, the transmission mechanism comprises a screw, the worm wheel is connected with the screw, a nut is connected with the screw through an external thread, a rack is processed on the outer surface of the nut and meshed with the gear teeth on the gear sector, the gear sector is connected with the rocker arm shaft, and the rocker arm shaft is connected with the output rocker arm.

Preferably, the transmission mechanism comprises an integrated worm, the worm wheel is connected with the integrated worm, the integrated worm is meshed with the integrated worm wheel, and the integrated worm wheel and the rocker arm shaft are integrally formed.

Preferably, the transmission mechanism comprises a herringbone driving gear, the worm gear is connected with the herringbone driving gear, the herringbone driving gear is meshed with a herringbone driven gear, and the herringbone driven gear and the rocker shaft are integrally formed.

Preferably, the input shaft is connected with the torsion bar through a spline or a pin, and the other end of the torsion bar is installed in the hollow cavity of the screw rod through the spline.

Preferably, the motor adopts an 6/4-pole switched reluctance motor, the rated voltage of the motor is 540V, the rated rotating speed is 20000r/min, the rated power is 3000W, and a natural cooling mode is adopted.

Preferably, the torque and rotation angle signal processing circuit is configured to process 4 frequency signals output by the torque and rotation angle sensor 2 and send the processed signals to the CPU, the 4 frequency signals are processed by the same processing circuit, and the motor winding temperature sensor in the motor winding temperature signal processing circuit is an NTC negative temperature coefficient resistor, one end of the NTC negative temperature coefficient resistor is connected to a 5V power supply, and the other end of the NTC negative temperature coefficient resistor is connected to the motor winding temperature signal processing circuit.

Preferably, a CAN signal transceiver of the CAN communication circuit adopts an isolation chip ISO1050, a power supply adopts an isolation chip ISD-B0505D, a connection end of the CAN signal transceiver and the CPU adopts a power supply for supplying power with the CPU, a connection end of the CAN signal transceiver and the external interface adopts an isolation power supply for supplying power, and a common-mode inductor B82790S513N201 and a resistor connected with 120 ohms in parallel are connected between a CAN high signal line and a CAN low signal line in series.

Preferably, the CPU and the FPGA in the CPU and FPGA processor circuit adopt a 32-bit digital signal processor TMS320F28335 and a field programmable gate array XC7Z010 processor supporting floating point operations.

Preferably, the SiC logic driving protection circuit is made of silicon carbide, the MOSFET in the three-phase asymmetric half-bridge power conversion circuit is made of silicon carbide, the withstand voltage level is 1200V, and the maximum drain current is 13A, and the schottky diode is also made of silicon carbide, the withstand voltage level is 1200V, and the maximum on current is 20A.

The invention has the advantages that:

1. the speed of the rotating speed of the motor can be adjusted according to a vehicle speed signal, the torque of the motor takes the steering wheel operating force as a signal, the size of the torsion bar corner is adjusted, and in order to realize the adjusting function of reducing speed and moment, the worm can be made into a single-head or multi-head scheme, and the axle load of a vehicle is taken as a basis; the screw nut adopts a transmission scheme of transmission threads, has the advantage of simple structure compared with ball screw transmission, can realize high positive efficiency and low reverse transmission efficiency through the optimized design of the transmission threads, and reduces the impact of the return positive impact of wheels and the impact of the attenuation of road vibration on a steering wheel.

2. Compared with hydraulic power assistance, the hydraulic power assistance device has the advantages of simple structure and high efficiency, saves sealing elements such as oil seals, oil ways and oil cylinders, simplifies the structure and reduces the cost; the motor controller and the motor are integrally designed to be connected with the shell or different shells, so that the space can be effectively reduced, the weight can be effectively reduced, the communication between the motor and the controller and the power line are internal wiring, and wiring harnesses are omitted; the sensor and the connector are integrated on the steering engine shell, so that the connecting structure is simplified, and the connection with the controller is more reliable.

3. The scheme that the screw rod and the nut are integrated has the characteristics of reliable transmission, small free gap and high positive transmission efficiency, and saves an original spiral transmission pair.

4. The motor is designed to use a high-speed switched reluctance motor to reduce the volume of the motor, has compact and firm structure, high temperature resistance and good mechanical stress of a rotor, is very suitable for the harsh requirements of the whole vehicle on the reliability and the volume of a steering system, adopts special trapezoidal groove shape and asymmetric winding arrangement in the design, leads the contact between a motor winding and the side surface and the bottom surface of an iron core groove to be more tight, leads the full rate of the winding groove to reach the optimal design value, improves the utilization rate of motor materials and improves the cooling performance of the motor.

5. The motor controller hardware adopts a third-generation semiconductor silicon carbide power device to form a three-phase asymmetric half bridge for driving the motor, so that the switching frequency of the control is doubled compared with that of the traditional controller, the switching loss is low, the size and the mass of the controller are reduced, the energy consumption of the whole vehicle is finally reduced, and the endurance mileage is improved.

Drawings

FIG. 1 is a side view of the apparatus of the present invention;

FIG. 2 is a top view of the apparatus of the present invention;

FIG. 3 is a schematic view of the internal structure of the torsion bar portion of the apparatus of the present invention;

FIG. 4 is a schematic view showing the internal structure of the shaft portion of the rocker arm in the apparatus of the present invention;

FIG. 5 is a schematic view showing the internal structure of the output shaft portion of the motor in the apparatus of the present invention;

FIG. 6 is a schematic view of the worm and worm wheel integrated in the device of the present invention;

FIG. 7 is a schematic view of a herringbone driving gear and a herringbone driven gear in the device of the present invention;

FIG. 8 is a schematic view of the motor windings and the asymmetric arrangement in the apparatus of the present invention;

FIG. 9 is a schematic diagram of the hardware of the switched reluctance motor controller in the apparatus of the present invention

The device comprises an input shaft, a torque and rotation angle sensor, a motor, a connector, a steering gear, a motor, an output rocker arm, a controller, a torsion bar, a screw rod, a motor output shaft, 11, a worm, 12, a worm gear, 13, external threads, 14, a nut, 15, internal threads, 16, a rack, 17, a sector, 18, gear teeth, 19, a rocker shaft, 20, an integrated worm, 21, an integrated worm gear, 22, a herringbone driving gear, 23 and a herringbone driven gear.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

As shown in fig. 1 to 9, an intelligent electric power steering system for a commercial vehicle is characterized by comprising an input shaft 1, a torque and rotation angle sensor 2, a motor 3, a steering gear 5, an output rocker arm 6 and a controller 7, wherein the input shaft 1 is connected with a torsion bar 8 in the steering gear 5, the other end of the torsion bar 8 is installed in a hollow cavity of a screw rod 9, the torque and rotation angle sensor 2 is connected with the controller 7 and is used for detecting the deformation quantity of the torsion bar 8, the motor 3 and the output rocker arm 6 are connected outside the steering gear 5, and the controller 7 is connected with the motor 3;

the front section of a motor output shaft 10 of the motor 3 is set to be a worm 11, the worm 11 is meshed with a worm wheel 12, the worm wheel 12 is connected with a screw rod 9, a nut 14 is connected with the screw rod 9 through external threads, a rack 16 is processed on the outer surface of the nut 14, the rack 16 is meshed with gear teeth 18 on a sector 17, the sector 17 is connected with a rocker shaft 19, and the rocker shaft 19 is connected with the output rocker arm 6;

the motor 3 adopts a switched reluctance motor, the controller 7 comprises a main control circuit and a three-phase asymmetric half-bridge power conversion circuit, the main control circuit comprises a torque and corner signal processing circuit, a bus current/voltage/phase current sampling circuit, a motor winding temperature signal processing circuit, a CAN communication circuit, a CPU and FPGA processor circuit, a motor position signal processing circuit, an overcurrent and overvoltage signal comparison circuit, an analog chopper circuit, a high-end driving and diagnosis circuit and a SiC logic driving protection circuit, and the three-phase asymmetric half-bridge power conversion circuit is formed by coupling a three-phase left half-bridge, a three-phase right half-bridge, a filter capacitor C1, an anode contactor S1, a precharge contactor S2 and a precharge resistor R1.

The screw rod 9 and the nut 14 can also adopt an integrated design, the screw rod 9 and the nut 14 are designed into an integrated worm 20, the gear sector 17 is designed into an integrated worm wheel 21 meshed with the worm 20, and the integrated worm wheel 21 and the rocker shaft 19 are integrally formed. The scheme has the characteristics of reliable transmission, small free gap and high positive transmission efficiency, saves the original spiral transmission pair and is convenient to process.

The screw rod 9 and the nut 14 can also adopt an integrated design, the screw rod 9 and the nut 14 are designed into a herringbone driving gear 22 with a shaft, the sector 17 is designed into a herringbone driven gear 23, and the herringbone driven gear 23 and the rocker shaft 19 are integrally formed. The scheme has the characteristics of reliable transmission, small free gap and high positive transmission efficiency, saves the original spiral transmission pair and is convenient to process.

The input shaft 1 is connected with a torsion bar 8 through a spline or a pin, and the other end of the torsion bar 8 is arranged in a hollow cavity of a screw rod 9 through a spline. When the angle and torque of the steering wheel reach a certain value, the torsion bar 8 deforms to a certain extent, and the angle and torque sensor 2 transmits a signal to the steering controller 7.

The motor 3 adopts an 6/4-pole switched reluctance motor, the rated voltage of the motor is 540V, the rated rotating speed is 20000r/min, the rated power is 3000W, and a natural cooling mode is adopted. The motor has compact and firm structure, high temperature resistance and good mechanical stress of a rotor, is very suitable for severe requirements of the whole vehicle on the reliability and the volume of a steering system, adopts special trapezoidal groove shape and asymmetric winding arrangement in the design, leads the motor winding to be more closely contacted with the side surface and the bottom surface of an iron core groove, leads the actual groove filling rate to be more than 65 percent, leads the winding groove filling rate to reach the design optimal value, improves the utilization rate of motor materials and improves the cooling performance of the motor.

The torque and rotation angle signal processing circuit processes 4 paths of frequency signals output by the torque and rotation angle sensor 2 and then sends the processed signals to the CPU for use, and the processing circuits of the 4 paths of frequency signals are the same. The method comprises the steps that the original signals from the sensor are firstly filtered to remove high-frequency interference through magnetic beads BKP1825HS600-T, the signals are pulled up through a pull-up resistor, then the signals pass through a second-order filter composed of a resistor and a capacitor, finally the signals subjected to second-order filtering are subjected to amplitude limiting and shaping through a TVS diode, and the signals are output to a frequency interface of a CPU.

The motor winding temperature sensor in the motor winding temperature signal processing circuit is an NTC negative temperature coefficient resistor, one end of the sensor is connected with a 5V power supply, and the other end of the sensor is connected with the motor winding temperature signal processing circuit. Firstly, the voltage is divided by a pull-down resistor and subjected to capacitance filtering, and then the amplified voltage is sent to an analog port of a CPU after being followed by TLV 2374.

The CAN signal transceiver of the CAN communication circuit adopts an isolation chip ISO1050, the power supply adopts an isolation chip ISD-B0505D, the connection end of the CAN signal transceiver and the CPU adopts a power supply for supplying power with the CPU, the connection end of the CAN signal transceiver and the external interface adopts an isolation power supply for supplying power, and a common-mode inductor B82790S513N201 and a resistor which is connected with 120 ohms in parallel are connected between a CAN high signal line and a CAN low signal line in series.

The CPU and the FPGA in the CPU and FPGA processor circuit adopt a 32-bit digital signal processor TMS320F28335 supporting floating point operation and a field programmable gate array XC7Z010 processor. Wherein, CPU is used for: carrying out preprocessing tasks such as analysis, signal validity confirmation, software filtering, redundancy check and the like on a sensor signal transmitted by a CAN bus; carrying out bottom layer driving processing on the analog signals and the digital signals; managing a system power supply; sensor fault diagnostics, etc. The FPGA processor is mainly used for: carrying out digital processing on the high-speed motor position signal; the power device is controlled by a high-speed control signal generated through the SiC logic driving circuit, the controlled switching frequency is up to 50KHz, and meanwhile, the power device is diagnosed and protected in real time through a feedback signal of the SiC logic driving circuit and a feedback signal of the motor phase current.

The SiC logic drive protection circuit adopts the carborundum material, MOSFET adopts the carborundum material among the asymmetric half-bridge power conversion circuit of three-phase, withstand voltage level 1200V, maximum drain current 13A, the carborundum material that schottky diode all adopted, withstand voltage 1200V, maximum conduction current 20A.

The specific implementation mode and principle are as follows:

the input shaft 1 is connected with a torsion bar 8 through a spline or a pin, and the other end of the torsion bar 8 is arranged in a hollow cavity of a screw 9 through the spline; when the turning angle and the moment of the steering wheel reach certain values, the torsion bar 8 deforms to a certain degree, the torque and turning angle sensor 2 transmits signals to the steering wheel controller 7, the controller 7 controls the power-assisted motor 4 to work through the signals and outputs torque and rotating speed, one section of a motor output shaft 10 of the motor 3 is made into a worm 11, the integrated design of the motor output shaft 10 and the worm 11 is realized, and the motor output shaft 10 and the worm 11 are connected together to form a connection which cannot move relatively or an integrated structure.

The torque and the rotating speed of the motor 3 are transmitted to the worm wheel 12 through the meshing transmission of the worm 11 and the worm wheel 12, so that the effects of reducing speed and increasing torque are realized; the worm wheel 12 transmits the torque to the screw rod 9, the outer surface of the screw rod 9 is provided with a transmission external thread 13, the inner surface of the nut 14 is provided with a transmission internal thread 15, the rotation of the screw rod 9 is converted into the translation of the nut 14 along the axial direction of the screw rod 9 through the meshing transmission of the external thread 13 and the internal thread 15, the outer surface of the nut 14 is provided with a rack 16, the rack 16 is meshed with the gear teeth 18 on the sector 17, the movement of the rack 16 is converted into the rotation of the sector 17 and the rocker arm shaft 19 through the meshing transmission of the rack 16 and the sector 17, the sector 17 and the rocker arm shaft 19 are designed into a whole, and the rotation of the rocker arm 19 is transmitted to a steering knuckle through a steering pull rod to drive.

In order to obtain large torque and required rotating speed, a screw transmission pair and a gear-rack transmission pair consisting of the screw 9, the nut 14 and the gear sector 17 are integrated into a worm gear transmission pair, so that the structure is simplified, and a large transmission ratio can be obtained, and the specific structure is shown in fig. 6 and 7.

The solution in which the screw 9 and the nut 14 are integrated: 1. the original nut 14 is integrated on the screw rod 9 to be designed into a worm 20, the sector 17 in the original design is designed into a worm wheel 21, and the worm wheel 21 and the rocker shaft 19 are designed into an integrated structure; 2. the original nut 14 is integrated on the screw to be designed into a driving herringbone gear 22, the sector 17 in the original design is designed into a driven herringbone gear 23, and the driven herringbone gear 23 and the rocker shaft 19 are designed into an integrated structure; the scheme has the characteristics of reliable transmission, small free gap and high positive transmission efficiency, saves the original spiral transmission pair and is convenient to process.

The motor 3 is designed to use a high-speed switched reluctance motor to reduce the volume of the motor, the motor 3 has compact and firm structure, high temperature resistance and good mechanical stress of a rotor, and is very suitable for the harsh requirements of the whole vehicle on the reliability and the volume of a steering system. The more the pole number of the rotor of the reluctance motor, the higher the fundamental frequency f, the higher the design difficulty of the controller, the higher iron loss and the lower the motor efficiency, and the comprehensive consideration adopts 6/4 pole structural design, the 540V motor, the rated rotation speed of 20000r/min, the rated power of 3000W and the natural cooling mode. The tooth profile of the motor rotor is designed into trapezoidal teeth, the arc (degree) of the stator tooth is 12 degrees, and the tooth root (degree) of the stator is 12 degrees; the tooth profile of the motor stator is designed into trapezoidal teeth, the pole arc (degree) of the rotor teeth is 13 degrees, and the tooth root (degree) of the tooth top and the rotor is 18 degrees.

The motor controller hardware comprises a main control circuit and a three-phase asymmetric half-bridge power conversion circuit:

the control circuit comprises a torque and corner signal processing circuit, a bus current/voltage/phase current sampling circuit, a motor winding temperature signal processing circuit, a CAN communication circuit, a CPU and FPGA processor circuit, a motor position signal processing circuit, an overcurrent and overvoltage signal comparison circuit, an analog chopper circuit, a high-end driving and diagnosis circuit and a SiC logic driving protection circuit.

The torque and corner signal processing circuit is characterized in that 4 paths of frequency signals output by a torque and corner sensor are processed and then sent to a CPU for use, the 4 paths of frequency signals are identical in processing circuit, original signals from the sensor are firstly filtered to remove high-frequency interference through magnetic beads BKP1825HS600-T, the signals are pulled up through a pull-up resistor, then the signals are subjected to amplitude limiting and shaping through a second-order filter composed of a resistor and a capacitor, and finally the signals subjected to second-order filtering are output to a frequency interface of the CPU through a TVS diode.

A bus current/phase current sampling circuit outputs a bus current and phase current sampling resistance signal to an isolation optocoupler AMC1200-Q1, and the signal is converted into a stable analog signal which can be received by a CPU through an operational amplifier TLC 4502.

The bus voltage adopts a circuit, firstly, high voltage supplied by a motor is divided by a resistor, then the high voltage is filtered by a capacitor, then the high voltage is converted into a differential signal by an isolation optocoupler AMC1200-Q1, and the differential signal is converted into a stable analog signal which can be received by a CPU by an operational amplifier TLC 4502.

The motor winding temperature signal processing circuit is characterized in that a motor winding temperature sensor is an NTC negative temperature coefficient resistor, one end of the motor winding temperature sensor is connected with a 5V power supply, the other end of the motor winding temperature sensor is connected with the motor winding temperature signal processing circuit, voltage division and capacitance filtering processing is firstly carried out through a pull-down resistor, and then the voltage is sent to an analog port of a CPU after being followed through TLV2374 operational amplifier voltage.

CPU and FPGA processor circuit, CPU adopts 32 digit signal processor TMS320F28335 and field programmable gate array FPGAXC7Z010 processors that support floating point operation, the dominant frequency is up to 600 MHz. Wherein, CPU is used for: carrying out preprocessing tasks such as analysis, signal validity confirmation, software filtering, redundancy check and the like on a sensor signal transmitted by a CAN bus; carrying out bottom layer driving processing on the analog signals and the digital signals; managing a system power supply; sensor fault diagnostics, etc. The FPGA processor is mainly used for: carrying out digital processing on the high-speed motor position signal; the power device is controlled by a high-speed control signal generated through the SiC logic driving circuit, the controlled switching frequency is up to 50KHz, and meanwhile, the power device is diagnosed and protected in real time through a feedback signal of the SiC logic driving circuit and a feedback signal of the motor phase current.

The motor position signal processing circuit processes A, B, C three paths of Hall signals and two paths of orthogonal coding signals, the output circuits of the motor position signal processing circuit are the same, and the signals firstly pass through a pull-up resistor and then pass through a first-order filter consisting of a resistor and a capacitor and then are sent to an FPGA processor for use.

The analog current chopping and current protection circuit is characterized in that a PWM signal is given by a reference signal of analog chopping through a DSP, the signal is enhanced through a driving chip SN74ACT244 and then is filtered through a second-order filter composed of TL028, the signal is converted into an analog signal, the analog signal and a processed phase current signal are compared through a comparator LM293, and a comparison result is sent to an FPGA for processing. Meanwhile, in order to prevent the comparator from generating jitter at the output of the vicinity of the set chopping current value, the comparator adopts a hysteresis loop form. Meanwhile, the processed phase current signal is compared with an over-current setting value GL, and when the phase current is greater than the over-current setting value GL, a low level is output to the FPGA through comparison so as to take corresponding protection measures.

The high-end driving and diagnosing circuit drives a direct current bus positive electrode contactor and a pre-charging contactor, a control signal of the DSP is firstly enhanced through an SN74ACT244, and after passing through an AND gate, a relay is driven, and the low level is effective.

The SiC logic driving protection circuit drives a three-phase asymmetric power circuit by using an British flying 2ED020I12-F2,1200V double-high-side gate driver integrated circuit, and has the functions of current isolation, desaturation protection, short circuit clamping and the like.

The three-phase asymmetric half-bridge power circuit comprises a U-phase left half-bridge composed of a SiC MOSFET T1 and a SiC Schottky D1, a U-phase right half-bridge and the left half-bridge are the same in structure, a V-phase and a W-phase are the same in structure, a filter capacitor C1, an anode contactor S1, a pre-charging contactor S2 and a pre-charging resistor R1. Preferably, the SiC MOSFET adopts British Rabbit IMW120R220M1H, the voltage resistance level is 1200V, and the maximum drain current is 13A, and the SiC Schottky diode adopts British IDW20G120C5B, the voltage resistance is 1200V, and the maximum conducting current is 20A.

Based on the above, the invention is composed of the novel steering gear, the high-rotating-speed high-power motor and the high-voltage motor controller, the traditional hydraulic power assisting device is not needed, the power source of the steering gear directly comes from the motor, and the novel steering gear, the high-rotating-speed high-power motor and the high-voltage motor controller are designed in a highly integrated manner, so that the space and the weight are saved. The novel motor is developed to meet the requirement of a steering system on low speed and large torque; a motor control system is developed, so that a driver can accurately control the motor to work in real time according to actual steering requirements by the electric control system; the development motor control system can communicate with other electronic control systems and can execute torque or angle control commands.

It will be appreciated by those skilled in the art that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed above are therefore to be considered in all respects as illustrative and not restrictive. All changes which come within the scope of or equivalence to the invention are intended to be embraced therein.

Claims

1. An intelligent electric power-assisted steering system of a commercial vehicle is characterized by comprising an input shaft (1), a torque and rotation angle sensor (2), a motor (3), a steering machine (5), an output rocker arm (6) and a controller (7), the input shaft (1) is connected with a torsion bar (8) in the steering gear (5), the other end of the torsion bar (8) is arranged in a hollow cavity of the screw (9), the torque and rotation angle sensor (2) is connected with the controller (7), and is used for detecting the deformation quantity of the torsion bar (8), the motor (3) and the output rocker arm (6) are connected outside the steering gear (5), the controller (7) is connected with the motor (3), the front section of a motor output shaft (10) of the motor (3) is set as a worm (11), the worm (11) is meshed with a worm wheel (12), and the worm wheel (12) is connected with the output rocker arm (6) through a transmission mechanism;

the motor (3) adopts a switched reluctance motor, the controller (7) comprises a main control circuit and a three-phase asymmetric half-bridge power conversion circuit, the main control circuit comprises a torque and corner signal processing circuit, a bus current/voltage/phase current sampling circuit, a motor winding temperature signal processing circuit, a CAN communication circuit, a CPU and FPGA processor circuit, a motor position signal processing circuit, an overcurrent and overvoltage signal comparison circuit, a simulation chopper circuit, a high-end driving and diagnosis circuit and a SiC logic driving protection circuit, and the three-phase asymmetric half-bridge power conversion circuit is formed by coupling a three-phase left half-bridge, a three-phase right half-bridge, a filter capacitor C1, an anode contactor S1, a precharge contactor S2 and a precharge resistor R1.

2. The intelligent electric power steering system of the commercial vehicle as claimed in claim 1, wherein: the transmission mechanism comprises a screw rod (9), the worm wheel (12) is connected with the screw rod (9), a nut (14) is connected with the screw rod (9) through an external thread, a rack (16) is processed on the outer surface of the nut (14), the rack (16) is meshed with gear teeth (18) on a sector (17), the sector (17) is connected with a rocker arm shaft (19), and the rocker arm shaft (19) is connected with an output rocker arm (6).

3. The intelligent electric power steering system of the commercial vehicle as claimed in claim 1, wherein: the transmission mechanism comprises an integrated worm (20), the worm wheel (12) is connected with the integrated worm (20), the integrated worm (20) is meshed with an integrated worm wheel (21), and the integrated worm wheel (21) and the rocker shaft (19) are integrally formed.

4. The intelligent electric power steering system of the commercial vehicle as claimed in claim 1, wherein: the transmission mechanism comprises a herringbone driving gear (22), the worm gear (12) is connected with the herringbone driving gear (22), the herringbone driving gear (22) is meshed with a herringbone driven gear (23), and the herringbone driven gear (23) and the rocker arm shaft (19) are integrally formed.

5. The intelligent electric power steering system of the commercial vehicle as claimed in claim 1, wherein: the input shaft (1) is connected with the torsion bar (8) through a spline or a pin, and the other end of the torsion bar (8) is installed in a hollow cavity of the screw (9) through the spline.

6. The intelligent electric power steering system of the commercial vehicle as claimed in claim 1, wherein: the motor (3) adopts an 6/4-pole switched reluctance motor, the rated voltage of the motor is 540V, the rated rotating speed is 20000r/min, the rated power is 3000W, and a natural cooling mode is adopted.

7. The intelligent electric power steering system of the commercial vehicle as claimed in claim 1, wherein: the torque and corner signal processing circuit is characterized in that 4 paths of frequency signals output by the torque and corner sensor (2) are processed and then sent to a CPU for use, the 4 paths of frequency signals are identical, a motor winding temperature sensor in the motor winding temperature signal processing circuit is an NTC negative temperature coefficient resistor, one end of the motor winding temperature sensor is connected with a 5V power supply, and the other end of the motor winding temperature signal processing circuit is connected with the motor winding temperature signal processing circuit.

8. The intelligent electric power steering system of the commercial vehicle as claimed in claim 1, wherein: the CAN signal transceiver of the CAN communication circuit adopts an isolation chip ISO1050, the power supply adopts an isolation chip ISD-B0505D, the connection end of the CAN signal transceiver and the CPU adopts a power supply for supplying power with the CPU, the connection end of the CAN signal transceiver and the external interface adopts an isolation power supply for supplying power, and a common-mode inductor B82790S513N201 and a resistor which is connected with 120 ohms in parallel are connected between a CAN high signal line and a CAN low signal line in series.

9. The intelligent electric power steering system of the commercial vehicle as claimed in claim 1, wherein: the CPU and the FPGA in the CPU and FPGA processor circuit adopt a 32-bit digital signal processor TMS320F28335 supporting floating point operation and a field programmable gate array XC7Z010 processor.

10. The intelligent electric power steering system of the commercial vehicle as claimed in claim 1, wherein: the SiC logic drive protection circuit adopts the carborundum material, the MOSFET adopts the carborundum material among the three-phase asymmetric half-bridge power conversion circuit, withstand voltage level 1200V, maximum drain current 13A, what the schottky diode adopted also is the carborundum material, withstand voltage level 1200V, maximum on-current 20A.