Method for waking up a steering control unit

Abstract

Method for waking up a steering control unit comprising a control device and a motor, in which a rotor position of a rotor of the motor (12) is monitored and, in the event that a change in the rotor position is detected, the steering control unit is woken up.

Description

[0001] The invention relates to a method for waking up a steering control unit (SCU) and an arrangement for carrying out the method. State of the art

[0002] A steering control unit (SCU) typically comprises a control unit and an electric motor. Such an SCU is typically used in an actuated steering or power steering system, in which a motor is used to apply additional torque to assist the steering movement. The SCU's control unit calculates the steering assistance and uses this information to control or regulate the electric motor. The power assistance is therefore calculated in the control unit. This calculation is not only dependent on the steering torque at the steering handle, e.g., a steering wheel, but also on other vehicle parameters. The steering control unit also serves as an interface to other control units in the vehicle.

[0003] In a steer-by-wire steering system, the steering control unit (SCU) must wake up during the park state to lock the steering wheel in case the steering wheel is moved by a person or vibration, resulting in the steering wheel not rotating freely.

[0004] Known methods provide for the steering control unit to be woken up by monitoring and detecting the so-called back EMF voltage generated by the motor due to the steering wheel torque.

[0005] Back EMF is an electromotive force (EMF) that occurs when a motor, especially a brushless motor, rotates. The motor acts like a generator, creating electromotive resistance.

[0006] In the idle state, a comparator monitors the back-EMF voltage at a motor phase terminal against a voltage threshold. When the comparator outputs a high-level signal, the steering control unit wakes up.

[0007] It should be noted that the back EMF voltage generated by the motor at low motor speeds, e.g. less than 20 rpm, is very small and becomes relatively inaccurate due to the motor tolerances.

[0008] Furthermore, environmental influences such as temperature, humidity, transients from the vehicle's electrical system, and EMC interference caused by neighboring electronic components or traffic must be taken into account in the automotive environment. As a result, a small back EMF voltage is superimposed on an interference voltage of approximately the same magnitude, which can have a wide frequency range and therefore cannot be easily filtered out.

[0009] Therefore, it is difficult to implement such a small voltage threshold and hysteresis with tight tolerances for the comparator. The noise causes the comparator to either switch to the high state or not switch at all due to the high tolerance of the voltage threshold. This back-EMF voltage-based wake-up function does not work reliably under all conditions, especially at low speeds, and a reliable solution would be prohibitively expensive.

[0010] The document DE 10 2020 206 435 A1 describes a method for influencing a movement of a steering handle of a steer-by-wire steering system in a vehicle. The steer-by-wire steering system comprises at least one feedback actuator for generating a steering resistance and / or a restoring torque on the steering handle. In at least one operating state in which the vehicle is stationary and in a passive operating mode different from a normal driving mode, the steering resistance and / or the restoring torque of the feedback actuator is adjusted and / or changed by means of a simulation function in response to an external force acting on the steering handle in such a way that a behavior of the steering handle correlated with a drilling and / or tire restoring torque is simulated.

[0011] A protective device for a vehicle's power steering system is known from DE 10 2006 040 689 B3. The power steering system comprises an electric servomotor connected to an evaluation circuit that registers a signal generated by the rotary movement of the servomotor when the ignition is off and activates a control and / or regulating device with an integrated braking function, which decelerates the electric servomotor. Disclosure of the invention

[0012] Against this background, a method according to claim 1 and an arrangement having the features of claim 8 are presented. Embodiments emerge from the dependent claims and from the description.

[0013] The presented method is used to wake up a steering control unit (SCU) based on the absolute rotation angle of the rotor shaft of a motor, in particular a synchronous motor with permanent magnets. The steering control unit comprises a control unit and a motor, and the rotor position of a rotor of the motor is monitored. For this purpose, for example, the position of a rotor shaft of the motor rotor is monitored. If a change in the rotor position is detected, the steering control unit is woken up.

[0014] The power assistance is calculated in a steering control unit. This calculation is based not only on the steering torque at the steering handle, e.g., a steering wheel, but also on other vehicle parameters. The steering control unit (SCU) also serves as an interface to other control units in the vehicle. The SCU typically comprises a control unit and an electric motor. The control unit calculates the steering assistance and uses this information to control the electric motor.

[0015] The method is based on the realization that any rotor movement can be detected by recording the rotor angle change with the rotor position sensor. The system base chip is equipped with a rotor position sensor interface that can record the number of rotor rotations using a counter in the sleep state. Each counter value (count) corresponds to a change of 90° in the rotor position. A comparator monitors the counter. If the counter is incremented or decremented by 2 or more, i.e., a movement of 180° or more, the comparator goes high and wakes up the system.

[0016] The presented method has, at least in some of the embodiments, a number of advantages: accidental waking can be prevented, Back-EMF detection in combination with rotor position detection makes the SCU wake-up function more effective and reliable, an SCU standby power requirement can be met, There are no additional implementation costs, as this function is fully digital and also uses the rotor position sensor already available in the system, The method meets wake-up requirements for a range of applications, such as a steering wheel actuator (SWA) and a steering rack actuator (SRA), the wake-up function is independent of the motor type and its BEMF levels (BEMF: Back emf voltage) generated by the motor, SPI configurability (SPI: Serial Peripheral Interphase) makes the process very flexible, The method can be used to detect very slow movements.

[0017] The presented arrangement comprises an evaluation unit configured to carry out the method described herein. The arrangement can be implemented in hardware and / or software. Furthermore, the arrangement can be integrated into a control unit or configured as such. Furthermore, the arrangement can be integrated into a control unit of a steering control unit or configured as such.

[0018] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0019] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention. Short description of the drawings Fig. 1 shows a block diagram of an embodiment of the presented arrangement. Fig. 2 shows a flow chart of a possible sequence of the presented procedure. Fig. 3 shows a schematic, highly simplified representation of a vehicle with an embodiment of the described arrangement. Fig. 4 shows a steering control unit in a block diagram. Embodiments of the invention

[0020] The invention is illustrated schematically in the drawings using embodiments and is described in detail below with reference to the drawings.

[0021] Fig. Figure 1 shows a block diagram of one embodiment of the presented arrangement, which is designated overall by the reference numeral 10. The illustration also shows a motor 12 and a rotor position sensor 14. The arrangement includes a sensor supply 20, a signal processor 22, a rotor position counter (SIN & COS) 24, a digital comparator 26, a first analog comparator 30, a second analog comparator 32, and a monostable multivibrator (retriggerable one-shot) 34. In this case, a trigger pulse sets the output to high. This high state remains for a fixed period of time, even if no input trigger signal is present. Each time the trigger pulse is applied, the timer is restarted. Since the back-EMF signal is transient, the output of the comparator 30 is no longer kept constantly high by the signal itself.Instead, the monostable multivibrator 34 switches on the wake-up circuit 60 and the sensor supply for a fixed period of time for signal processing.

[0022] The input of monostable multivibrator 34 is connected to the output of OR gate 50. A high at the output of OR gate 50 is generated, either by a high from analog comparator 30 or by a high at the output of SIN / COS counter 24, which indicates a change in the counter reading. A high at output 50, in turn, generates a high with a defined time at the output of monostable multivibrator 34.

[0023] The output of the monostable multivibrator 34 is connected to an OR gate 62. The sensor can be woken up either by a back-EMF signal or a periodic wake-up function.

[0024] The output of OR gate 62 switches on the sensor's power supply. This means that the sensor is supplied with energy and evaluated by signal processing 22. The rotor position is then updated via the SIN / COS counter 24. The digital comparator 26 is set to high when the rotor position counter 24 matches a defined threshold in the comparison register 70.

[0025] The ASIC is woken up when the output of the OR gate 62 and the output of the digital comparator 26 are high.

[0026] The presented method is used to wake up the SCU at a precise rotor speed, especially when the rotor speed is low, e.g. less than 20 rpm.

[0027] For this purpose, the rotor position counter 24 is provided, which increments or decrements by 1 for every 90° rotation of the rotor. An increment occurs when the rotor rotates clockwise, and a decrement occurs when the rotor rotates counterclockwise. In the sleep state, the ASIC periodically powers up the sensor supply and checks each rotor movement, updating the counter when a rotor movement is detected. If the ASIC detects a predefined number of increments or decrements in the rotor position counter 24, which is configurable via SPI during the sensor wake-up phases, the ASIC will fully wake up.

[0028] If the rotor is rotating at a high speed, the ASIC will miss some rotor position counts and wake up at a later rotor position than the predetermined one. In this case, the conventional back-EMF voltage detection function will wake up the ASIC.

[0029] Fig. Figure 2 uses a flowchart to describe a possible sequence of the presented method. In a first step 100, a steering control unit of a vehicle's steer-by-wire steering system is in a rest state. The rotor position is monitored. If a change in this rotor position that exceeds a threshold value is detected in step 102, the steering control unit is awakened in step 104.

[0030] Fig. Figure 3 shows a schematic, highly simplified representation of a vehicle, designated overall by reference numeral 150. This vehicle 150 comprises a steer-by-wire steering system 152, to which a steering control unit 154 is assigned, which in turn has a control unit 156 and a motor 158. Furthermore, an arrangement 160 with an evaluation unit 161 is provided, which monitors the rotor position of a rotor shaft 162 of a rotor 164 in the motor 158 and is configured to wake up the steering control unit 154 upon detecting a change in position.

[0031] Fig. Figure 4 shows a block diagram of a steering control unit, designated overall by reference numeral 200. This steering control unit 200 is connected to a steering wheel 202.

[0032] The illustration shows a system base chip 210 connected to a microcontroller 212 via an SPI interface 214 and a power connection 216. Furthermore, a rotor position sensor 220 is provided, which in turn is connected to the system base chip 210 via a power connection 222 and a SIN / COS signal connection 224.

[0033] Furthermore, an output stage driver 230 is provided, which is also connected to the system base chip 210 via a supply connection 232 and to the microcontroller 212 via a signal connection 234. The output stage driver 230 controls the output stage switches 240 (six in total), in this case MOSFETs, which in turn control the motor phases 250, 252, 254 of a motor 256. One or more signals relating to the back EMF voltage 258 are returned to the system base chip 210 from one or more connections of the motor phases 250, 252, 254.

[0034] A rotor 260 includes a rotor magnet 262 that provides an input signal 264 regarding the rotor position of the rotor 260 to the rotor position sensor 220. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 206 435 A1

[0010] DE 10 2006 040 689 B3

[0011]

Claims

[1] A method for waking up a steering control unit (154, 200) comprising a control device (156) and a motor (256), in which a rotor position of a rotor (164, 260) of the motor (12, 158, 256) is monitored and in the event that a change in the rotor position is detected, the steering control unit (154, 200) is woken up. [2] Method according to claim 1, wherein the steering control unit (154, 200) is awakened when the temporal change of the rotor position is above a threshold value. [3] Method according to claim 2, wherein the temporal change is compared with the threshold value by means of at least one comparator (30, 32). [4] Method according to claim 3, wherein the at least one comparator (30, 32) triggers the wake-up. [5] Method according to one of claims 1 to 4, wherein a number of rotations of the rotor (164, 260) is counted with a counter (24). [6] Method according to one of claims 1 to 5, which is carried out in a permanent magnet synchronous motor. [7] Method according to one of claims 1 to 6, in which a back EMF voltage is additionally monitored in order to wake up the steering control unit (154, 200) if necessary. [8] Arrangement for waking up a steering control unit (154, 200) with an evaluation unit (161) which is designed to carry out a method according to one of claims 1 to 7. [9] Arrangement according to claim 8, which is integrated in a system base chip (210). [10] Arrangement according to claim 8 or 9, which is configurable via a serial peripheral interface (SPI).

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