Steering arrangement

Abstract

Steering arrangement comprising a housing (4), a steering control device (1) and an angle detector, which includes an electric motor (11) with motor windings (7) and a motor control device, wherein the rotor of the motor (7) is operatively connected to the steering control device (1) and can be operated as a generator, characterized in that the motor control device derives an angle signal from magnetic properties of the electric motor (11), wherein the electric motor (11) is a multipole motor having at least two groups of motor windings (7), and the motor control device has a corresponding number of motor controls.

Description

The present invention relates to a steering arrangement comprising a housing, a steering control device and an angle detector, which includes an electric motor with motor windings and a motor control device, wherein the rotor of the motor is operatively connected to the steering control device and can be operated as a generator. Such a steering arrangement is known from the generic patent DE 198 20 774 A1. When the steering control device is actuated, the motor operates as a generator and produces a voltage proportional to the speed of the motor's rotor, which also contains information about the direction. This signal can then be integrated to specify an angular position. The integration of a speed signal to specify a position is not an absolute reference value. This means that the position can drift even if the angle is not physically changed. In a steering arrangement, it is very important to have an absolute position. JP H11-125537 A describes a steering angle sensor for a vehicle. The sensor incorporates an electric motor coupled to a steering handwheel, which generates a multi-phase output signal. This output signal is an alternating voltage corresponding to a specific electromotive force. The steering direction can be derived from the phase relationship of the alternating voltages. By counting the wavenumbers of the alternating voltages, the steering angle can be calculated. The object underlying the invention is to obtain information about the absolute angle of the steering control device in a simple way. This problem is solved by a steering arrangement having the features of claim 1. One way to obtain angular information, i.e., information about the angular position of the motor's rotor, is described in US 6,448,725 B1. However, in the steering arrangement according to embodiments of the present invention, the motor is used without activating it, i.e., without driving it. The motor is used to provide a sensor output instead of using a signal to control the motor, as in US 6,448,725 B1. The sensor output signal can also be used outside the sensor. For example, it can be sent on a CAN bus in a vehicle to be steered by the steering arrangement and can be used for other purposes on that vehicle. If the electric motor is a multipole motor, this has the advantage of increasing the resolution of the signal representing the angular position of the steering device. The more poles available, the better the resolution.If the electric motor has at least two sets of motor windings and the motor control unit has a corresponding number of motor controls, it is possible to make the steering arrangement functionally safe by splitting the motor windings into at least two independent motor controls. This provides full redundancy for position sensing and, if force feedback is used, half power redundancy for force feedback. In one embodiment of the invention, the magnetic properties are derived by measuring voltage and / or current. This can be the waveform of the voltage and / or current generated by the motor during a rotation caused by movement of the steering control device. It is also possible to supply electrical energy to the motor with or without activating it, i.e., without rotating it or with the generation of a feedback force, and to measure the response of the supply voltage and / or current to the generated voltage and / or current. In one embodiment of the invention, the motor control unit has a drive mode in which the electric motor is supplied with electrical energy. In this way, it is possible to use the motor to generate force feedback to the steering control unit. If force feedback is desired, the angular position of the steering control unit is obtained free of charge, without the need for a separate sensor. In one embodiment of the invention, the electric motor has at least twelve pole pairs. This allows a resolution of 30° per pole pair. In a preferred embodiment, the electric motor has eighteen pole pairs. In one embodiment of the invention, an angle sensor is provided in addition to the angle detector, wherein the angle sensor detects a steering angle specified by the steering control device. The angle sensor and the angle detector perform practically the same function, i.e., they detect the steering angle specified by the steering control device. The steering angle is transmitted to a rotational position of the motor rotor, which the angle detector can detect. Furthermore, it is possible to detect the steering angle of the steering control device directly at the steering control device. In one embodiment of the invention, the angle sensor is arranged radially within the motor windings. Therefore, the angle sensor requires little to no additional space. In one embodiment of the invention, the angle sensor comprises a transducer / receiver assembly fixed to the housing and a target assembly rotatably mounted on the steering control device, which includes a passive response arrangement. This means that only passive parts are attached to the movable part of the steering control device and, for example, rotate when the steering control device is actuated. It is possible, for instance, to use a transducer / receiver assembly that generates a high-frequency electric field to produce a resonant response in the target. When the target is excited into resonance, it generates a counter-field that can be received by the receiver of the transducer / receiver assembly. The received signal can be split into a sine component and a cosine component. From these two components of the signal, it is possible to detect the angle of a steering control device. In one embodiment of the invention, the steering control device comprises a wheel having a rim and a shaft, wherein the rim interacts with the motor and the shaft interacts with the angle sensor. In this way, it is possible to acquire information about the absolute angle of the steering handwheel from two different positions on the wheel. In one embodiment of the invention, the electric motor is a brushless direct current (BLDC) motor. In a brushless DC motor, information about the angular position of the rotor is necessary to control the motor's operation. This information can now be used to output a commanded steering angle, i.e., the angle specified by the steering control device. One embodiment of the invention will now be described in more detail with reference to the drawing, wherein: Fig. 1 shows a schematic cross-sectional view of a steering control device and Fig. 2 shows a perspective view of parts of the steering control device from below. Fig. 1 schematically shows a steering control device 1, which is part of a steering assembly. In the present embodiment, the steering control device 1 is in the form of a steering handwheel, more precisely in the form of a mini steering handwheel 2. The mini steering handwheel 2 has a shaft 3 which is rotatably mounted in a housing 4. Furthermore, the mini steering handwheel 2 has a rim 5 which extends parallel to the shaft 3. Within the rim is a stator 6 of a brushless DC motor (BLDC) 11. The stator 6 is also mounted in the housing 4 and is therefore stationary. The stator 6 has a number of stator windings 7. Two stator windings 7 together form a pole pair. As can be seen in Fig. 2, the brushless DC motor has 18 pole pairs corresponding to 36 motor windings. The edge 5 carries a corresponding number of permanent magnets 8. The housing is mounted on an armrest 9 of a vehicle that is controlled by the steering arrangement. In a manner not shown, the windings 7 of the stator 6 are connected to a motor control unit. In the present embodiment, the motor control unit has two motor controllers, each motor controller being connected to one half of the windings 7, i.e., one half of the pole pairs of the motor. When the mini steering handwheel 2 is rotated relative to the housing 4, a current is induced in each winding 7. If, as in the present embodiment, the number of pole pairs is a multiple of three, a three-phase current and a corresponding three-phase voltage can be generated, with an electrical offset of 120° between the phases. It is therefore possible to derive information about the angular position of the steering handwheel 2 relative to the housing 4 by comparing the respective output signals. One way to achieve this result is disclosed in US 6,448,725 B1. In the present embodiment, however, the motor is not activated, i.e., it is not controlled by the motor control unit to rotate; rather, the motor control unit merely evaluates the voltages and / or currents induced by a rotation of the mini steering handwheel 2 relative to the housing 4. In other words, by measuring the voltage and / or current induced in the windings, it is possible to detect the magnetic properties of the electric motor and derive the angular position information from the magnetic properties. In a brushless DC motor, information about the rotor's position relative to the stator is necessary for correct control. In this case, this information can be used to obtain the desired steering angle, i.e., the angular position of the mini steering wheel 2 relative to the housing 4. The two motor controls make the steering control device 1 functionally safe, as they provide full redundancy in position detection. Furthermore, the motor control unit can be operated to supply electrical energy to the motor. When electrical energy is supplied to the motor, force feedback can be generated to signal to the driver of the vehicle that external forces are acting on the steered wheels. If the brushless DC motor is used for this purpose, the angular information is obtained free of charge. In addition to the motor, which acts as an angle detector, an angle sensor 10 is provided. The angle sensor 10 is connected to the shaft 3 of the mini steering handwheel 2 and detects a steering angle specified by the mini steering handwheel 2. As can be seen in Fig. 1, the angle sensor 10 is arranged radially inside the motor windings and, in the present embodiment, radially inside the stator 6. In a manner not shown, the angle sensor 10 has a target connected to the shaft 3 of the mini steering wheel 2. A portion of the angle sensor connected to the housing 4 has a transducer / receiver arrangement comprising at least one excitation coil as a transducer and a pair of receiving coils as a receiving device. Accordingly, the target is a passive reaction arrangement with no active components. When the excitation coil is supplied with a high-frequency voltage, e.g., 2 MHz, it generates an electric field that induces a current in the target coil. This current generates a counter-field that is detected by the receiving coils. As mentioned above, the motor control unit has two motor controllers. This means that the unit is made functionally safe by splitting the windings 7 into two independent motor controllers. This provides full redundancy for position sensing and half power redundancy for force feedback. If the motor 11 has two groups of motor windings 7 connected to two separate motor controllers, an extra angle sensor 10 can be omitted. The described principle can also be used in conjunction with joysticks and conventional steering handwheels. When a mini steering handwheel 2 is used, a preferred embodiment of the motor 11 is a flat pancake motor with many poles. A joystick will typically require a longer motor with a smaller diameter, and a conventional steering handwheel with a large diameter can be used together with a motor with many poles. A mini steering handwheel 2 typically has 16, 24, 30, 36, or 42 poles. A control stick prefers 6, 12, 18, or 24 poles, and a steering handwheel prefers 36, 42, 48, 54, 60, 66, or 72 poles.

Claims

Steering arrangement comprising a housing (4), a steering control device (1) and an angle detector, which includes an electric motor (11) with motor windings (7) and a motor control device, wherein the rotor of the motor (7) is operatively connected to the steering control device (1) and can be operated as a generator, characterized in that the motor control device derives an angle signal from magnetic properties of the electric motor (11), wherein the electric motor (11) is a multipole motor having at least two groups of motor windings (7), and the motor control device has a corresponding number of motor controls. Steering arrangement according to claim 1, characterized in that the magnetic properties are derived by voltage and / or current measurement. Steering arrangement according to claim 1 or 2, characterized in that the motor control device has a drive mode in which the electric motor (11) is supplied with electrical energy. Steering arrangement according to one of claims 1 to 3, characterized in that the electric motor (11) has at least twelve pole pairs. Steering arrangement according to one of claims 1 to 4, characterized in that an angle sensor (10) is provided in addition to the angle detector, wherein the angle sensor (10) detects a steering angle given by the steering control device (1). Steering arrangement according to claim 5, characterized in that the angle sensor is arranged radially within the motor windings (7). Steering arrangement according to claim 5 or 6, characterized in that the angle sensor (10) has a transmitter / receiver arrangement attached to the housing (4) and a target arrangement which is rotationally fixed to the steering control device (1) and has a passive reaction arrangement. Steering arrangement according to one of claims 5 to 7, characterized in that the steering control device (1) has a wheel (2) with a rim (5) and a shaft (3), wherein the rim (5) interacts with the motor (11) and the shaft (3) interacts with the angle sensor (10). Steering arrangement according to one of claims 1 to 8, characterized in that the electric motor (11) is a brushless DC motor.

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