JPH08331799A - Motor controller for motor-driven power steering - Google Patents

Abstract

PURPOSE: To form a time lag before manual operation is returned and to deal with the weight of a handle by reversely rotating two motors, rotating the planetary arm of a differential unit by the rotating difference, and assisting the steering. CONSTITUTION: The rotor shafts 21, 22 of first and second motors 101, 102 are respectively connected to the rotary shaft of the internal gear 2 and the rotary shaft of the sun gear 4 of a differential unit 103. A pinion gear 1 in which the gear 4 is brought into inner contact with the gear 2 outputs the rotation of a planetary arm 3 for supporting the gear 1 by rotating around the gear 4 while rotating around its own axis, and the arm 3 is connected to a torque transmission shaft 23. Thus, since the two motors 101, 102 are rotated at high speed, a time lag before manual operation is returned by its kinetic energy, i.e., inertial torque can be formed. Further, the control of making a handle 19 heavy during driving at high speed can be easily formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects information on vehicle speed and steering torque in an electric power steering system of an automobile, calculates an assist amount and an assisting direction based on the information, and controls the electric motor by using the information as input information. The present invention relates to a motor control device for electric power steering that power assists steering.

[0002]

2. Description of the Related Art Conventionally, a hydraulic control system has been generally used to drive a power steering, but it has advantages such as a compact structure, no engine output consumption, and fine control of steering torque. Steering power assist has become widespread. However, there were some problems that power assist by electric motor did not occur in hydraulic control. One is overheating and damage due to overheating of the electric motor, which hydraulic pressure did not have to worry about. If the handle is locked and held at the maximum turning angle, current will continue to flow due to the load on the motor, causing overheating of the motor, and further damage to the motor and wasted power due to increased current load. At this time, it is necessary to control to cut off the current and perform relief. Another issue is how to relieve when a large kickback force, which is a reaction force from the road surface, acts on the electric motor and a large load is applied to it. In this case, it is necessary to provide a control and mechanism such as detecting that a large external reaction force is applied to the motor and performing relief using a mechanism such as a clutch. Even if the motor machinery part can be protected by the relief, the power assist is relieved by a large reaction force, so that the steering wheel suddenly becomes heavy and the driver is panicked, which is dangerous. The other is fail-safe when the electrical system is suddenly short-circuited. Although there is a similar failure in hydraulic pressure, in the case of hydraulic pressure, there is a time lag before returning to manual operation because the hydraulic pressure gradually decreases, and the driver can handle the weight of the steering wheel. In the case of the electric drive, the steering wheel suddenly fails and returns to the manual operation, so that the steering wheel suddenly becomes heavy and confuses the driver as described above.
Further, in the case of a conventional electric motor, when it is used after being greatly decelerated, a motor lock (mechanical lock) due to a failure occurs. You also need to release this. Further, the reaction force control for stabilizing the steering wheel during high-speed traveling, that is, the control for making the steering wheel heavy cannot be easily realized by the power assist by the electric motor.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and controls the electric current of the motor to be cut off for relief even if the handle is locked and held at the maximum turning angle. It is possible to drive without needing it, and it is possible to drive the motor without the need for relief even when a large kickback force, which is a reaction force from the road surface, acts on the electric motor and a large load is applied. The steering wheel does not suddenly become heavy and confuses the driver, and even in the case of fail-safe when the electrical system suddenly shorts, it is possible to create a time lag before returning to manual operation like hydraulic pressure. Can respond. Also, the structure can prevent the motor lock from occurring. Further, it is possible to easily realize the control of making the steering wheel heavy during high-speed driving. An object of the present invention is to provide a motor control device for such electric power steering.

[0004]

An assist motor for performing power assist of an electric power steering device is a first
A motor and two motors, a second motor, and a differential gear are provided, and the differential gear is a planetary gear (planetary gear).
The rotation axes of the sun gear and internal gear are
Each is connected to the rotating shafts of the first and second motors. Also,
A control device for controlling the two motors is provided, and the control device performs switching and torque control of whether to drive or regenerate the two motors according to the input information of the assist amount and the rotation direction, and reverses the two motors. A motor control device for an electric power steering, which is rotated, and a pinion gear of a differential device revolves due to a rotation difference between the two motors, and steering is assisted by rotation of a planetary arm that supports the pinion gear. I will provide a. Further, a differential gear including a side gear, a pinion gear, a pinion shaft and the like may be used as the differential device. In that case, the rotary shafts of the two left and right side gears of the differential device are connected to the rotary shafts of the first and second motors, respectively, and the steering of the pinion gear is supported by the rotation of the pinion shaft. Further, the rotating wheel of the planetary arm may be directly connected to the steering shaft of the steering wheel input shaft. Further, a reduction mechanism that reduces the rotation can be provided between the differential device and the motor.

[0005]

In the case of an electric motor, especially a high-performance DC motor, since the internal resistance is small, an excessive current may flow at a rotational speed of 0 and damage the motor. In addition, power loss is also large and causes overheating. Judging from the characteristics of the motor, if it can be rotated at a high speed without being affected by the output speed, it will not cause overcurrent even when the output is 0 rotation, which will prevent damage to the motor due to overheating and waste of electric power. It is possible to keep the motor running even if a large kickback (reaction force) is applied. The motor device of the present invention causes two motors to rotate in opposite directions via a differential device, and outputs the differential rotation from the differential device, and the output serves as a driving force for assisting steering. Therefore, even if the output rotation is 0, the two motors can rotate at high speed. That is, since the output is connected via the differential device, two motor rotations can be set independently of the output rotation. For example, when the differential ratio (the ratio of the rotation difference between the first motor and the output of the differential gear and the rotation difference between the second motor and the output of the differential gear) is 1: 1, and the output is 0, the first motor has a speed of 2000 rpm. If it is rotated by rotation, the second motor will rotate in reverse at a speed of 2000 minutes.
It can be rotated by rotation. In addition, the first motor has a speed of 1 minute
If the rotation speed is 000, the second motor will rotate in reverse at 100 rpm.
It only needs to be 0 revolutions. Further, even if the output has a large reaction force such as kickback, it can be absorbed by the differential device. This is also because the motor is rotating at a much higher speed than the output rotation, and even a large reaction force has little influence because the motor itself can rotate at high speed. Further, even if the motor suddenly fails, the motor is rotating at a high speed, so that the kinetic energy, that is, the inertia torque, can make a time lag before returning to the manual operation. Also, there is little concern about motor lock. This is because the motor can rotate at a high rotation speed without deceleration, and the motor does not greatly decelerate even in a free state due to a failure, so that the motor can be easily rotated manually. In addition, it is possible to easily create a control that makes the steering wheel heavy during high-speed driving. This is because it is easy to change the direction and amount of output torque without changing the rotation directions of the two motors.

The operation of the electric power steering motor controller of the present invention will be described below. First, the relationship between the first and second motors and the torque and rotational speed of the drive output is expressed by the following equation. In the differential device according to the present invention, the ratio of the differential gears, that is, the differential ratio is X. If the ratio of the differential device is 1: 1 then X = 1, if 2: 1 then X =
It becomes 2. The second motor side X is the second motor side 1. If the torque and the rotational speed of the first motor are T ₁ and N ₁ , the output torque and the rotational speed of the output rotary shaft are T ₂ and N _2, and the consumed torque and the rotational speed of the second motor are T ₃ N ₃ , It looks like this: (X + 1) T ₁ = T ₂ …………………… (1) (N ₁ −XN ₃ ) / (X + 1) = N ₂ …… (2) Therefore, the mechanical output from the first motor is , Rotation speed (rpm) x torque, unless considering the loss due to friction
T ₁ · N ₁ , and the mechanical input from the second motor is rotational speed (rpm) × torque, which is T ₃ · N ₃ . Therefore, the mechanical output of the output of the differential is the number of rotations (rpm).
× Torque, which is T ₂ · N ₂ . Therefore, T ₂ · N ₂ = T ₁ · N ₁ −T ₃ · N ₃ (3) Therefore, when the drive shaft torque is X = 1,
Although the torque of the drive motor (first motor) is twice, the rotation speed of N ₂ is the rotation speed of the first motor when the output of the second motor is 0, that is, when the second motor does not rotate. 1/2 (X = 1). The relationship between the input and output torques of the first motor and the second motor is XT ₁ = T ₃ …………………… (4). Next, how the two motors generate the output rotation / torque in association with each other will be described. First, an operation example of power assist will be briefly described. For example, if you want to assist the power in the same direction when turning the steering wheel to the right (to make it lighter), the motor that rotates in the same direction as the steering wheel (rotates to the right) (2
Since the two motors rotate in opposite directions to obtain driving force, there is one motor that rotates to the right and one motor that rotates to the left)
Is operated as a drive motor, and the motor that rotates in the opposite direction to the direction you want to assist is regenerated as a generator motor, the motor rotation load at the time of regeneration causes another differential rotation to the motor that is rotating (driving right). A load is applied via the motor, and the driving force of the motor in the same direction as the steering rotation is transmitted to the output, torque (rotational force) is generated in the same direction (right rotation), and power assist can be performed. Similarly, if you want to assist the power in the same direction when turning the steering wheel to the left (lightening), you can do the reverse of the above.
Operate the counterclockwise rotation motor as a drive motor. Similarly to the above, the driving force from the differential device is transmitted to the output, torque (rotational force) in the reverse direction (counterclockwise rotation) is generated, and power assist is possible. Further, when the steering wheel is made heavy, that is, when the reaction force is controlled, the steering wheel can be made heavy by power assisting in a direction opposite to the direction in which the steering wheel is desired to be rotated. Even when a reaction force (kickback) is generated from the road surface, the power reaction in the direction of canceling the reaction force can reduce the reaction to the steering. From the above, it is possible to handle both right and left rotations with either heavy or light steering under the two conditions of generating torque in the right rotation or generating torque in the left rotation by controlling the two motors that are power assisted. Recognize. That is, which motor is used for driving, whether the output is right rotation or left rotation,
The rotation direction is changed depending on which motor is used for power generation. Whether the assisting output is clockwise or counterclockwise, one motor is operated as a drive motor and the other motor is operated as a generator motor, and its differential output is taken out by a differential device and used as an output. In this way, two motors are used, one of which is a drive motor and the other of which is a generator motor, and the two motors are reversely rotated through a differential device and the differential output thereof is used as an assist force. A more detailed explanation of this mechanism is given in the graph using numerical examples. (However, the numerical values are just examples and the numerical values themselves have no meaning.) To simplify the explanation, the rotation ratio of the differential gear is set to 1:
1 will be described. First, FIG. 1 showing a torque-rotation speed curve of the first motor (used as a drive motor) as a TN curve used only for the purpose of explanation is shown in FIG. FIG. 2 shows a curve of the consumed torque and the number of revolutions, which is used only for the explanation of the torque and the number of revolutions. Further, FIG. 3 shows a torque-rotational speed curve of the drive output shaft. As shown, the torque of the first motor decreases as the rotation speed increases, and the torque of the second motor increases as the rotation speed increases. Then, as shown in FIG. 3, the torque of the drive output shaft decreases as the rotation increases. The rotation speed of the drive output increases from left to right. Each point P corresponds to the point shown in each graph.

[Table 1] First, the output rotation is set to '0', and the rotation speed and torque of the first motor and the second motor at this time are calculated by the formula (X = 1
The first and second motors are balanced at the same torque and the same rotational speeds P1 and P2. (However, mechanical loss is not considered) At this time, the output shaft is the first motor
Torque of 10kg ・ m (P1) is doubled to 20kg ・ m
The torque of (P3) is generated. (Equation (X + 1) T ₁ =
Than T _2). Also, at this time, the output rotation is "0", so the first
Since the drive energy of the motor becomes the energy for power generation of the second motor, there is less energy loss (because the power generation energy can be regenerated). (Expression, 0
= T ₁ · N ₁ −T ₃ · N ₃ ). At this time, the number of revolutions
Even if a high torque of 0 ″ of 20 kg · m (P3) is generated, since the first motor is actually rotating, overcurrent does not occur and normal operation is possible. Next, the rotation speed of the output shaft Is 1000 rpm (P6), the rotational speed and torque of the drive motor and generator motor are as follows:
When the ratio is 1: 1, both the drive motor and the generator motor have the same torque and balance. Therefore, from the formula, the drive motor has a rotation speed of 3000 rpm and a torque of 5 kg-m (P4). It becomes rotation)
It is 1000 rpm and the torque is 5 kg-m (P5). At this time, the output shaft torque is 5 kg of the drive motor torque.
Torque (P6) of 10kg-m which doubled -m (P4)
Is obtained. Similarly, when the drive motor is (P7), the power generation motor is (P8) and the output is (P9). In this way, the drive motor (TN
The curve), the generator motor (TN curve in FIG. 2) and the drive output (output shaft) are balanced, and the output of the TN curve as shown in FIG. 3 is obtained.

As described above, even when the output rotation is 0 and the load is high, the motor can rotate at high speed to prevent overcurrent, and moreover, by directly regenerating the generated power to the drive motor, the power consumption is saved and the drive current is also reduced. It can also increase the load on the battery and reduce the voltage drop due to the internal resistance of the battery. While having such excellent characteristics, the output characteristics can be made the same as one single motor. Further, there is no problem in using the two motors by decelerating them by using the speed reducing mechanism. In this case, the same applies when decelerating only the first motor or decelerating only the second motor. Next, the control of the assist amount will be described. Naturally, the assist amount can be controlled by controlling the power supply (voltage) of the drive side motor. This is similar to conventional motor control, but in this control, the efficiency of the control device directly affects the output of the drive motor. For example, when the output is controlled by a variable resistance device and the assist amount is adjusted, the supplied power is consumed by the resistor. Therefore, it is necessary to devise a consumption circuit that is electronically controlled such as PMW to reduce the consumption. Further, since the electric power on the driving side is handled, a large electric power control is performed and the control device becomes expensive. In the case of the motor device of the present invention, the control of the assist amount, that is, the control of the drive torque can be controlled by the amount of regenerative electric power of the power generation side motor instead of the drive side motor. This is because, as described above, the output torque is generated in proportion to the magnitude of the load torque of the generator motor. Therefore, it is possible to control the torque of the drive side motor by controlling the amount of regenerative electric power of the power generation side motor. This is because, as described above, the driving side motor stabilizes at a rotational speed that balances the load torque of the power generation side motor. Therefore, for example, even if the amount of electric power generated by the motor on the power generation side is controlled by the variable resistance device, the loss on the drive side does not occur because the control is not performed on the drive side motor. Further, since the electric power to be controlled is smaller than that of the driving side motor and the control efficiency need not be considered so much, the control device can be inexpensive.
Next, examples of the electric power steering motor control device of the present invention will be shown, but the present invention is not limited thereto.

[0008]

[Embodiment 1] An embodiment of the present invention will be described with reference to FIG. The vehicle speed information 11 of the vehicle speed sensor 105 and the input torque information 12 of the torque sensor 104 that detects the twist angle of a torsion bar (not shown) that connects the steering shaft 20 as the steering wheel input shaft and the torque transmission shaft 23, that is, the steering wheel steering torque amount. The control circuit 106 which uses as input information determines the regenerative power shown in FIG. 7 based on the vehicle speed information 11 and the input torque information 12 which are the input information. As shown in FIG. 7, the regenerative power signal 13 is output so that the regenerative power decreases as the vehicle speed increases and the regenerative power increases as the input torque increases. Further, the control circuit outputs the input torque information 1
Based on the information of the rotation direction of 2, the forward rotation, the reverse rotation, or the neutral is determined, and the rotation direction signal 16 is output. The regenerative power signal 13 becomes an input signal of the regenerative circuit 107. The regenerative circuit regenerates an amount of generated power proportional to the signal 13. Ie signal 1
3 is the power assist amount. The input power of the regenerative circuit 107 is the power generated from the motor and supplied from the regenerative power line 15 via the switch circuit. Then, the amount of power generated in proportion to the signal 13 is regenerated to charge the battery and supply the power to the power supply line 14. There are various methods for controlling the amount of regeneration of the regenerative circuit 107, but as an example, the generated voltage can be boosted at a boost rate proportional to the signal 13. In the case of this example, a signal voltage proportional to the power assist amount is output from the control circuit from the signal 13, the voltage proportional to the voltage is boosted by the regenerative circuit, and a backflow prevention circuit (not shown in the figure) is provided so that the backflow of regenerative power does not occur. Although it is not, the circuit built in the regeneration circuit will regenerate the battery and drive motor. The rotation direction signal 16 becomes an input signal of the switch circuit 108. The switch circuit includes first and second switch circuits.
A circuit for driving, regenerating or switching the motor, that is, connecting the terminals of the first and second motors to the power supply line 14 of the power supply device (battery) or the regenerative power line 15 of the regenerative circuit by the signal 16. It is a circuit that causes or switches. When the rotation direction signal 16 is the forward direction (the rotation direction of the first motor), the switch circuit first connects the first motor to the battery and rotationally drives it as a drive motor. When the rotation of the drive motor is increased, the second motor is connected to the regenerative circuit to operate as a generator motor. Since the first motor rotates in the forward direction and becomes a drive motor, the power can be assisted in the forward direction. When the rotation direction signal 16 is in the reverse direction (the rotation direction of the second motor) in the switch circuit, the second motor is first connected to the battery to be rotationally driven as the drive motor. When the rotation of the drive motor is increased, the first motor is connected to the regenerative circuit and operated as a generator motor. The second motor rotates in the opposite direction and becomes a drive motor, so that power assist can be provided in the opposite direction. Further, when the rotation direction signal 16 is neutral in the switch circuit, no assistance is provided in either direction, so that the two motors are in a state of being disconnected from the battery and the regeneration circuit, that is, in a power-off state (released state). By controlling the first motor and the second motor in this way, it is possible to reduce the steering force (power assist) that matches the vehicle speed. The first and second motors are DC brush motors,
A DC brushless motor (the driving device is included in the motor), an AC motor, or any motor can be used as long as it is in accordance with the gist of the present invention.
5 and 6 are views showing some examples of the differential gear of the present invention. FIG. 5 is a cross-sectional view schematically showing an example of the case where a planetary gear is used for the differential device. When the differential device of FIG. 5 is used for the differential device 103 of FIG. 4, the rotor shafts 2 of the first and second motors are
Planetary gears 1 and 22 are connected to the rotary shaft of the internal gear 2 and the rotary shaft of the sun gear 4, respectively, and the planetary gear 1 inscribed in the sun gear and the internal gear revolves while rotating to support the planetary gear 1. Arm 3
Is output, and the planetary arm is connected to the torque transmission shaft 23. FIG. 6 is a cross-sectional view schematically showing an example in which a differential gear is used in the differential device. When the differential device of FIG. 6 is used for the differential device 103 of FIG. 4, the rotor shafts 21 of the first and second motors are
22 are connected to the rotation shafts of the side gears 7 and 9, respectively, and the pinion gears 5 and 8 meshed with the side gears revolve while revolving on their own axis, and the rotation B of the pinion shaft 6 that supports the pinion gears becomes an output, and the pinion gears 8 are output. The shaft is supported by a support case (not shown), and the revolving rotation of the pinion shaft is the rotation of the support case, so that the rotation shaft and the torque transmission shaft 23 are connected. With such a configuration, the motor can rotate at high speed even when the output rotation is 0 and the load is high, and the power generated can be regenerated and directly regenerated by the drive motor to save power consumption and drive. The amount of current can be increased, and the current from the battery plus the regenerative current can be reduced to reduce the load on the battery.
Further, this can reduce the voltage drop due to the internal resistance of the battery.

[0009]

The present invention has the following technical effects due to the structure shown in the drawings. That is, even if the output of the power assist is 0 revolutions, overcurrent does not occur, motor damage due to overheating and waste of electric power are avoided, and the motor operates even if a large kickback (reaction force) is applied from the outside. It is possible to continue. Further, even if the output has a large reaction force such as kickback, it can be absorbed by the differential device. This is also because the motor is rotating at a much higher speed than the output rotation, and even a large reaction force has little influence because the motor itself can rotate at high speed. Also,
Even if the motor suddenly fails, since the motor is rotating at high speed, it is possible to create a time lag until the motor returns to the manual mode due to its kinetic energy, that is, inertia torque. Also, there is little concern about motor lock. This is because the motor can rotate at a high rotation speed without deceleration, and the motor does not greatly decelerate even in a free state due to a failure, so that the motor can be easily rotated manually. In addition, it is possible to easily create a control that makes the steering wheel heavy during high-speed driving. This is because it is easy to change the direction and amount of output torque without changing the rotation directions of the two motors. Also, while the motor is running,
There is less risk of motor damage due to large external loads. Even if the output rotation is stopped due to a large reaction force or kickback, or if the output rotation is reversed due to some external factors, the motor itself can rotate at high speed, so the motor can be operated while maintaining the rotation force. It is possible. In addition, during power assist, the drive current can be increased by directly regenerating the power generated by the generator motor to the drive motor, and the regenerative current is added to the current from the battery to reduce the current load on the battery. This also reduces the voltage drop due to the internal resistance of the battery.

[Brief description of drawings]

FIG. 1 is a graph showing a torque-rotation speed relationship of a first motor in an electric power steering motor control device of the present invention.

FIG. 2 is a graph showing a torque-rotational speed relationship of a second motor in the electric power steering motor control device of the present invention.

FIG. 3 is a graph showing a torque-rotation speed relationship of a power assist output in the electric power steering motor control device of the present invention.

FIG. 4 shows a configuration of an example of a motor control device for electric power steering of the present invention.

FIG. 5 is a sectional view showing an example of a planetary gear when the planetary gear is used as a differential device of the electric power steering motor control device of the present invention.

FIG. 6 is a cross-sectional view of an example of a differential gear when the differential gear is used as the differential device of the electric power steering motor control device of the present invention.

FIG. 7 is a graph showing the relationship between the assist amount, the vehicle speed, and the steering torque amount of the steering wheel of the electric power steering motor control device of the present invention.

[Explanation of symbols]

1 Pinion Gear 2 Internal Gear 3 Planetary Arm 4 Sun Gear 5, 8 Pinion Gear 6 Pinion Shaft 7, 9 Side Gear 19 Handle 20 Steering Shaft 21, 22 Motor Rotor Shaft and Differential Gear Rotation Shaft 24 Steering Gear Box 25 Tie Rod 26, 27 Left and right front wheels 101 First motor 102 Second motor 103 Differential device 104 Torque sensor 105 Vehicle speed sensor 106 Control circuit for controlling regenerative circuit and switch circuit 107 Regenerative circuit 108 Switch circuit

Claims (4)

[Claims] 1. An assist motor for performing power assist of an electric power steering device comprises two motors, a first motor and a second motor, and a differential device, and the differential device is a planetary gear (planetary gear). The rotation shafts of the sun gear and the internal gear are connected to the rotation shafts of the first and second motors, respectively. In addition, a control device for controlling the two motors is provided, and the control device performs switching and torque control for driving or regenerating the two motors according to the input information of the rotation direction and the assist amount to control the two motors. A motor for an electric power steering characterized in that the pinion gears of the differential device revolve around each other due to the rotation difference between the two motors, and that the steering of the planetary arm supporting the pinion gears assists the steering. Control device. 2. An assist motor for performing power assist of an electric power steering device comprises two motors, a first motor and a second motor, and a differential device, and the differential device is a differential gear. The rotation shafts of the two left and right side gears are connected to the rotation shafts of the first and second motors, respectively. In addition, a control device for controlling the two motors is provided, and the control device performs switching and torque control for driving or regenerating the two motors according to the input information of the rotation direction and the assist amount to control the two motors. Motor control for electric power steering characterized in that the pinion gears of the differential gear revolve due to the rotation difference between the two motors, and the steering of the pinion shaft that supports the pinion gears assists the steering. apparatus. 3. The motor device according to claim 1, wherein an output rotation shaft of the differential device is directly connected to a steering shaft of a steering wheel input shaft. 4. A speed reducer for reducing the rotation of the two or one motors is connected to the two or one motor rotary shafts, and is connected to the rotary shafts of the differential gears through the speed reducers. The motor device according to claim 1 or 2, characterized in that: