HARDWARE IMPLEMENTED MOTOR CONTROL AND PLATFORM FOR EPS

Abstract

A motor electric control unit (ECU) for an electromechanical power steering mechanism, which controls current through an electric assist motor in response to sensed vehicle signals, wherein the ECU comprises an application specific integrated circuit (ASIC) design, that implements safety and platform features in hardware.

Claims

1.-12. (canceled)

13. A motor electric control unit (ECU) for an electromechanical power steering mechanism, which is configured to control current through an electric assist motor in response to sensed vehicle signals, wherein the ECU comprises an application specific integrated circuit (ASIC) configured to implement safety and platform features in hardware.

14. The motor electric control unit of claim 13 wherein the ASIC circuit comprises a gate driver unit (GDU) supervision module, said GDU module configured to monitor the status of a power module and detect failures, and that comprises a pulse-width modulation unit for driving the electric assist motor.

15. The motor electric control unit of claim 13 wherein the ASIC circuit comprises a sensor interface circuit configured to interface with all sensors of the ECU.

16. The motor electric control unit of claim 13 wherein the ASIC circuit comprises a platform block configured to perform electric motor management, including start-up testing of paths and control of the electric motor in normal operation and a safety shutdown mode.

17. The motor electric control unit of claim 13 wherein the ASIC circuit comprises a motor control block configured to implement a core motor control algorithm.

18. The motor electric control unit of claim 13 wherein the ASIC circuit comprises a safety envelope block configured to implement a torque safety limiter function in order to ensure that a requested motor torque is in a safe range.

19. The motor electric control unit of claim 13 wherein the ASIC circuit comprises a backup block configured to implement a simple steering function in form of a boost curve, which defines the relationship between an indicated input torque and an assistance torque applied by the electric motor.

20. The motor electric control unit of claim 13 wherein parameters for functional blocks are set by an external MCU interface.

21. The motor electric control unit of claim 13 wherein the ASIC circuit is configured such that the ECU is usable used in different vehicles without hardware modification, wherein parameters thereof are changed by software solely.

22. The motor electric control unit of claim 13 wherein the ECU has two channels, with two ASIC circuits, one circuit for each channel.

23. The motor electric control unit according to claim 22 wherein the two channels share one external MCU.

24. An electromechanical power steering mechanism for assisting steering of a motor vehicle comprising an electric motor for steering assist and a torque sensor, the electric motor being configured to apply an assistance torque in response to an output signal from the torque sensor indicative of the input torque applied by a driver of the vehicle to a steering wheel, with a motor electric control unit (ECU) of claim 13.

Description

[0013] Exemplary embodiments of the present invention are described below with aid of the drawings. In all figures the same reference signs denote the same components or functionally similar components.

[0014] FIG. 1 shows a schematic illustration of a motor electric control unit according to the invention, and

[0015] FIG. 2 shows four preferred embodiments of the motor electric control unit according to the invention.

[0016] As shown in FIG. 1, the motor electric control unit (ECU) 1 has an application specific integrated circuit (ASIC) design, that implements safety and platform features in hardware. The ASIC platform 2 contains several functional blocks.

[0017] The lowest level is the GDU (gate driver unit) supervision module 3, that monitors the status of the MosFETs of the power module and detects all possible failures (FET short, FET cut, GDU not driving the FET correctly, FET in linear mode). The implementation is fully in hardware, in order to be able to react very quickly (range of a few microseconds) before a) a FET is damaged, or b) if after a FET fault a second consecutive fault occurs. This block 3 also contains the PWM generation block (not shown), that gets the voltage vector that shall be actuated, and emits the three phase PWM signal for the motor drive.

[0018] The next block of the ASIC is the sensor interface circuit 4. This block 4 is responsible for the interfacing of all sensors of the ECU, e.g. rotor position sensor, current measurement sensor, column torque sensor, steering wheel angle sensor, and temperature sensors. The sensors are preferably connected via analog signals, except for the torque and steering angle sensors, which use preferably SENT or SPC protocols. The implementation of this block converts the physical signals (analog or SENT/SPC) to an internal format and decodes the real values (current, angle, torque, temperature) from the electrical signal. The sensor diagnostics is advantageously fully implemented by hardware, for example a comparison between two channels in case of a dual channel system, a radius check for RPS, and range checks. The output of the module 4 is the qualified (reliable/not reliable/not available) signal set that can be used by further units:

[0019] The next block is called platform 5, and implements most of the functions that are currently done by the platform software. It receives the sensor signals from the above-mentioned sensor interfaces block 4, and uses these for further computations in hardware. It produces the electrical angle of the motor, the current vector out of the measured current samples, and based on the temperature, current, and motor speed, it calculates the necessary degradation (torque limit) degree. This block 4 is also responsible for the actuator management, which includes the start-up testing of the actuator paths (including GDU, FETs, and safety relays), and the control of the actuator in normal operation, and safety shutdown. Based on all diagnostics implemented in the blocks, it evaluates the necessary actions (ramp down assist, shut down actuator). It also contains a root cause analysis circuit to interpret the actual diagnostic picture. All these functions are preferably implemented in hardware.

[0020] The motor control block 6 is responsible for the implementation of the core motor control algorithm. This is a parallel PI structure consisting of two controllers (not shown). The input sensors' signals are supplied by the platform block 5, and the reference motor torque is supplied by a safety envelope block 7. The output of the block 6 is the voltage vector that is actuated on the motor. The actuation is done in the GDU block 3.

[0021] The safety envelope block 7 implements the torque safety limiter function. The input torque request from the steering application is received (running on an external, non safety rated MCU, which is not shown) and safety limitations are applied to it. The result is the reference torque request for the motor control. The main goal of the block 7 is to ensure that the requested motor torque is always in a safe range.

[0022] The backup block 8 is implementing a simple steering function that is able to provide assist even without an external MCU device. The control is a simple boost curve, relying on the input column torque, and an external boost look-up table.

[0023] All the blocks 3, 4, 5, 6, 7, 8 contain several parameters (like diagnostics limit, controller parameters, look-up tables) that can be set via an external MCU interface (not shown). Internally, these are stored in SRAM based registers, and protected with CRC and continuous checks. The aim of this solution is to be able to use the ASIC in different vehicles without hardware modification. This way, the basic safety measures are implemented in a stable hardware device, and only their parameters are changed by software.

[0024] Due to the hardware implementation, no revalidation is necessary for the safety functions in all releaseskdue to built-in quick diagnostics. The GDU 3 can be of arbitrary type. Safety is ensured by the ASIC. The MCU selection is made easier, as all safety functions are implemented in hardware. The motor control frequency can be arbitrary high, because the hardware can support any frequency (up to MHz range). This results in better NVH (Noise, vibration and harshness) and dynamic behavior. The built-in backup steering control 8 can give assist without a MCU. The cost and complexity of a second MCU can be avoided.

[0025] FIG. 2 shows four embodiments of the present invention. The different architectures can be built to meet diverse OEM requirements. All embodiments have in common that after the ASIC 2 a PM 9 is arranged, which actuates the calculated required motor currents for the electric motor 10.

[0026] Embodiment a) renounces to use an MCU. In contrast, embodiment b) has an MCU 11 upstream of the ASIC 2. The external MCU 11 can set the parameters for the blocks of the ASIC 2. Embodiments c) and d) have two channels, wherein in embodiment c) one MCU 11 for both channels is arranged upstream of the two ASICs 2,2 and wherein in embodiment d) two MCs 11,11 are used, one for each channel.