JP2008110629A - Method of tuning electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of tuning an electric power steering device capable of improving the efficiency of adjusting operations and cost required by calculating a rack thrust by a tuning device, inputting a target steering torque as a target during the traveling of a vehicle into the tuning device to calculate a necessary motor current value, and setting an assist map. <P>SOLUTION: The electric power steering device is tuned by the method comprising a step 1 of setting predetermined parameter values in the tuning device, a step 2 of inputting the target steering torque as a target into the tuning device, a step 3 of measuring a steering torque according to the measured values of a sensor system and estimating a rack thrust according to the measured steering torque, a step 4 of calculating a necessary motor current according to steps 1-3, and a step 5 of setting the assist map according to the necessary motor current and performing tuning. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tuning method of an electric power steering device that applies a steering assist force by a motor to a steering system of a vehicle, and in particular, setting of a necessary assist steering torque for a tuning unit and a control unit incorporated in an actual vehicle, The present invention relates to a tuning method for an electric power steering apparatus that can be calculated from rack thrust (tire reaction force) and adjust motor current to increase work efficiency in the adjustment process and to reduce costs.

  An electric power steering device for energizing a vehicle steering device with an auxiliary load by a rotational force of a motor applies an auxiliary load to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a reduction gear. It has come to force. Such a conventional electric power steering apparatus performs feedback control of motor current in order to accurately generate assist steering torque (steering torque). In the feedback control, the motor applied voltage is adjusted so that the difference between the current command value and the motor current detection value becomes small. Generally, the adjustment of the motor applied voltage is a duty of PWM (pulse width modulation) control. This is done by adjusting the tee ratio.

  Here, the general configuration of the electric power steering apparatus will be described with reference to FIG. 7. The column shaft 2 of the steering handle 1 is connected to the steering wheel via the reduction gear 3, the universal joints 4 a and 4 b, and the pinion rack mechanism 5. Coupled to the tie rod 6. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque Th of the steering handle 1, and a motor 20 that assists the steering force of the steering handle 1 is coupled to the column shaft 2 via the reduction gear 3. Has been. A power is supplied from the battery 14 to the control unit 30 that controls the power steering device, and an ignition signal is input through the ignition key 11. The control unit 30 detects the steering torque Th detected by the torque sensor 10 and the vehicle speed. An assist command steering assist command value I is calculated based on the vehicle speed V detected by the sensor 12, and a current supplied to the motor 20 is controlled based on the calculated steering assist command value I.

  The control unit 30 is mainly composed of a CPU (including MPU and MCU), and FIG. 8 shows general functions executed by a program inside the CPU.

  The function and operation of the control unit 30 will be described with reference to FIG. 8. The steering torque Th detected by the torque sensor 10 is input to the steering assist command value calculation unit 32. Further, the vehicle speed V detected by the vehicle speed sensor 12 is also input to the steering assist command value calculation unit 32. The steering assist command value calculation unit 32 determines a steering assist command value I that is a control target value of the current supplied to the motor 20 with reference to the assist map 33 based on the input steering torque Th and the vehicle speed V. The steering assist command value I is input to the subtraction unit 30A and is also input to the feedforward differential compensation unit 34 for increasing the response speed, and the deviation (Ii) of the subtraction unit 30A is input to the proportional calculation unit 35. At the same time, it is input to the integral calculation unit 36 for improving the characteristics of the feedback system, and its proportional output is input to the addition unit 30B. The outputs of the differential compensator 34 and the integral calculator 36 are also added to the adder 30B, and the current control value E, which is the addition result of the adder 30B, is input to the motor drive circuit 37 as a motor drive signal. The motor current detection value i of the motor 20 is detected by the motor current detection unit 38, and the motor current detection value i is input to the subtraction unit 30A and fed back.

  When adjusting the steering torque Th output from the electric power steering apparatus as described above, a simulation is performed before the adjustment work by the actual vehicle, and a target target steering torque is determined in advance to set the assist map 33. Then, the target steering torque set in the assist map 33 and the actually output steering torque Th are compared by a test driver using an actual vehicle. Then, the test driver confirms the magnitude of the steering torque Th that is actually output from the actual vehicle, adjusts the steering assist command value I so that the target steering torque is output, and causes the vehicle to travel again. The steering torque Th that is actually output is confirmed and adjusted. In addition, such adjustment work is generally performed at each vehicle speed (for example, 10 km / h of 10 to 80 km / h) at a predetermined steering angular speed (for example, 30 deg / sec) that is less affected by the steering angular speed or motor inertia. The steering torque Th to be output is adjusted in an arbitrary range of each steering angle (for example, every 5 degrees of −25 to 25 degrees).

  As described above, the steering torque Th output from the electric power steering apparatus is adjusted by adjusting the steering assist command value I so that the test driver outputs the steering torque Th that improves the feeling during traveling of the vehicle. It is carried out. That is, in the tuning method of the electric power steering apparatus, the steering assist command value I is adjusted so that the target steering torque Th is output by the trial and error by the test driver.

  In such a conventional electric power steering device tuning method, the adjustment process takes a lot of time and a special measuring instrument (load cell or the like) is used to calculate the rack thrust (tire reaction force). It will be up.

An apparatus disclosed in Japanese Patent Laid-Open No. 2005-59688 (Patent Document 1) includes a steering force characteristic control unit that controls a steering force characteristic, a vehicle response characteristic control unit that controls a vehicle response characteristic of a vehicle, and a desired steering fee. A steering feeling setting means for setting a ring, and the steering feeling setting means is configured such that when the steering wheel is turned from a straight traveling state at a predetermined vehicle speed or higher, the steering force characteristic is always substantially constant regardless of the change in the vehicle speed. The steering force control means and / or the vehicle response characteristic control means are controlled. In other words, the steering feeling (steering force characteristics) is quantified according to the vehicle environment, and the steering feeling felt by the driver is almost constant regardless of changes in vehicle speed, steering speed, vehicle weight, and road surface conditions. The torque is adjusted.
JP 2005-59688 A

  However, the apparatus of Patent Document 1 uses a lateral acceleration sensor, a rudder angle sensor, a yaw rate sensor, a vehicle weight sensor, a road surface resistance sensor, and the like, resulting in an increase in cost and a complicated configuration that is particularly detected. The rack thrust (tire reaction force) from the road surface is only an estimate, and there is a problem that it is not used for adjusting the steering torque output by the electric power steering device.

  The present invention has been made under the circumstances described above, and an object of the present invention is to invalidate (zero) the output of each compensation system (phase compensation, inertia compensation, convergence control, etc.) provided in the electric power steering apparatus. The rack thrust during vehicle travel is estimated by the tuning device from a sensor system provided in a general electric power steering device without using a special sensor or measuring instrument. The tuning device calculates the necessary motor current based on the detected steering torque, the calculated rack thrust, and the target steering torque input to the tuning device, and based on the calculated necessary motor current, It is an object of the present invention to provide an electric power steering apparatus tuning method capable of improving the efficiency and necessary cost of adjustment work by setting an assist map of a control unit and outputting an ideal steering torque.

  Also, after satisfying the target steering torque (after setting the required motor current in the assist map) with the output of each compensation system of the electric power steering device disabled, simulation of each compensation system output is performed by the tuning device. An object of the present invention is to provide a tuning method for an electric power steering apparatus that can optimize a steering assist command value and each compensation system by obtaining optimum parameters for each compensation system.

  The present invention calculates a steering assist command value based on an assist map provided in the control unit, and controls a motor that applies a steering assist force to the steering mechanism based on the steering assist command value. The present invention relates to a tuning method of an electric power steering apparatus that tunes the electric power steering apparatus with a tuning apparatus connected to the control unit. The object of the present invention is to set a predetermined parameter value in the tuning apparatus, and a target A step 2 for inputting the target steering torque to the tuning device, a step 3 for measuring the steering torque based on the measured value of the sensor system, and estimating a rack thrust based on the measured steering torque, and the step 1 to 4 for calculating a necessary motor current based on the above-mentioned step 3; Serial based on the required motor current is achieved by including the step 5 of tuning by setting the assist map.

  Further, by making the control value of each compensation system provided in the control unit zero and performing the tuning, or after the tuning, the control value of each compensation system based on the necessary motor current By performing simulation and optimizing the control values of the respective compensation systems based on the simulation, or the tuning device, based on the step 3, the steering torque Lissajous waveform diagram for the steering angle and the step 3, the rack thrust Lissajous waveform diagram for the steering angle is created, or in Step 2, the target steering torque is input to the steering torque Lissajous waveform diagram or the rack thrust Lissajous waveform diagram. This is achieved more effectively.

  According to the tuning method of the electric power steering apparatus of the present invention, the output of each compensation system provided in the electric power steering apparatus is invalidated without using a special sensor or measuring instrument, and is generally used for the electric power steering apparatus. The required motor current is calculated based on the steering torque detected by the tuning device, the rack thrust calculated by the tuning device, and the target steering torque input to the tuning device based on the detected value from the sensor system By setting the assist map, the efficiency of the adjustment work can be improved and the necessary cost can be reduced.

  In addition, the output of each compensation system of the electric power steering device is invalidated, and each compensation system output is simulated by the tuning device while satisfying the target steering torque, so that the steering assist command value and each compensation system can be optimized. It can be carried out.

  In the electric power steering device tuning method according to the present invention, the tuning device is connected to the control unit of the electric power steering device, and each compensation system (phase compensation, inertia compensation, convergence control, etc.) provided in the electric power steering device is provided. Is disabled (zero), and each vehicle speed (for example, 10 km / h of 10 to 80 km / h) at a predetermined steering angular speed (for example, 30 deg / sec) is less affected by the steering angular speed or motor inertia, which is generally regarded as important. In addition to measuring a steering torque and a motor current detection value that are detected in an arbitrary range of each steering angle (for example, every 5 deg of −25 to 25 deg) with respect to every h), a motor gear ratio, a pinion rack gear ratio, a worm gear efficiency, and a pinion Preset values such as rack gear efficiency are input to the tuning device and set. To. The tuning device calculates the rack thrust based on the measured value and the input set value, creates a rack thrust Lissajous waveform diagram (estimation diagram of tire reaction force against the steering angle) with respect to the steering angle at a predetermined vehicle speed, A steering torque Lissajous waveform diagram with respect to the steering angle at the vehicle speed (a diagram of the steering torque with respect to the output steering angle) is created. Then, the test driver or the person in charge of adjustment inputs the target steering torque into the steering torque Lissajous waveform diagram for the steering angle created by the tuning device. Next, the tuning device calculates a required motor current based on the detected steering torque, the calculated rack thrust, and the input target steering torque, and prepares for the control unit based on the calculated required motor current. Set the assist map provided.

  Further, in order to optimize the steering assist command value, the output of each compensation system of the electric power steering device is invalidated, and the target steering torque is satisfied (the assist map is set based on the necessary motor current). Then, each compensation system is simulated by the tuning device. The tuning device optimizes the steering assist command value based on the optimum parameters of each compensation system obtained by simulation, the target steering torque, and the necessary motor current.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing an example of the configuration of the present invention. The configuration of an apparatus for carrying out the present invention is obtained by adding a tuning device 40 to the electric power steering apparatus of FIG. The same parts as those in FIG.

  First, the tuning device 40 includes a CPU that performs overall control of the tuning device, a ROM that contains an operation program, a RAM that functions as a memory, a communication unit such as a LAN or RS232C that performs mutual communication with the control unit 30, and An input unit such as a mouse, a keyboard, or a touch panel operated by a person in charge of adjustment work, and a display unit for displaying calculation results and statuses are included. Further, the electric power steering device and the control unit 30 have the same configuration as the conventional one, and the description thereof is omitted.

  Then, the test driver or the person in charge of adjustment sets parameter values that can be obtained in advance, such as the motor gear ratio of the reduction gear 3, the pinion rack gear ratio of the pinion rack mechanism 5, and the pinion rack gear efficiency, in the tuning device 40.

  Next, the tuning device 40 is connected so that each control system of the control unit 30 and the assist map 33 can be set. Further, the steering angle θ, the steering angular velocity ω, the steering torque Th, the motor current detection value i flowing through the motor 20 and the like input to the control unit 30 are measured so as to be measured. Also, since it is ideal to make adjustments without being affected by each compensation system at the time of measurement, the output of each compensation system provided in the control unit 30 is turned off so as not to receive interference from each compensation system. In addition, the steering assist command value I is supplied to the motor 20, and the steering angle θ, the steering angular velocity ω, the steering torque Th, and the detected motor current value i flowing through the motor 20 are measured.

  The tuning device 40 calculates the rack thrust F based on the steering angle θ, the steering angular velocity ω, the steering torque Th, and the motor current detection value i from the sensor system, and the target steering torque input by the person in charge of adjustment work. The necessary motor current Imt is calculated based on Tmh and the rack thrust F, and the necessary motor current Imt is set in the assist map 33, so that the steering assist command value I satisfying the target steering torque Tmh is output to the motor 20. .

  FIG. 2 is a block diagram showing the signal and information paths in FIG. 1 in a simplified manner. The same parts are denoted by the same reference numerals, and description thereof is omitted.

  A detection signal of the steering torque Th, the steering angle θ, and the steering angular velocity ω is input to the control unit 30 from a sensor system provided in the steering handle 1 and is detected by a motor current detection unit 38 provided in the motor 20. The detected current value i is also input to the control unit 30. The steering torque Th, the steering angle θ, the steering angular velocity ω, and the detected motor current value i input to the control unit 30 are measured by the tuning device, and the rack thrust F is calculated based on the measured values and is input by the person in charge of adjustment work. The required motor current Imt is calculated based on the target steering torque Tmh and the calculated rack thrust F, and the assist map 33 is set based on the required motor current Imt.

  FIG. 3 is a flowchart showing an operation example of the present invention, and the present invention will be described with reference to this flowchart.

First, the test driver or the person in charge of adjustment work connects the tuning device 40 to the control unit 30 of the electric power steering device provided in the actual vehicle (step S10), and each compensation system (phase compensation, inertia compensation) of the electric power steering device. The output of the convergence control is invalidated (zero) by the tuning device 40 (step S11). Next, the test driver or the person in charge of adjustment presets the motor gear ratio Gr, the pinion rack gear ratio Cf, the pinion rack gear efficiency μ2, and the worm gear efficiency μ1 in the tuning device 40, and the steering angle θ from the steering angle sensor 11 is set by the tuning device. The steering angular velocity ω, the steering torque Th from the torque sensor 10, and the motor current detection value i from the motor current detector 38 can be measured. Each vehicle speed (for example, 10 km of 10 to 80 km / h) at a predetermined steering angular speed (for example, 30 deg / sec) less affected by the steering angular speed or motor inertia generally regarded as important by a test driver or an adjustment operator The steering torque Th and the motor current detection value i that are actually output are measured in an arbitrary range of each steering angle (for example, every 5 deg of -25 to 25 deg) (step S12). Here, based on the measured value and the set value in Step 12, the rack thrust F is calculated from the following rack thrust calculation formula (1) (Step S13).

F = (Th + Kt * Im * Gr * μ1) * 2π / Cf * μ2 * 1000 (1)

Based on the rack thrust F of the above equation (1), as shown in FIG. 4 as an example, a rack thrust Lissajous waveform diagram with respect to the steering angle is created in an arbitrary steering angle range (step S14).

  Next, based on the measured value of the actually output steering torque Th detected in step S12, a steering torque Lissajous waveform diagram for the steering angle is created in an arbitrary steering angle range as shown in FIG. 5 as an example ( Step S15).

Then, the target steering torque Tmh for each steering angle is input to the tuning device 40 with reference to the rack thrust Lissajous waveform diagram (FIG. 4) and the steering torque Lissajous waveform diagram (FIG. 5) displayed on the tuning device 40 ( Step S16). Here, the tuning device 40 calculates the necessary motor current Imt based on the target steering torque Tmh input in step S16. The required motor current Imt is calculated by the rack thrust F obtained from the above equation (1), the input target steering torque Tmh, the motor torque constant Kt, the motor gear ratio Gr, the worm gear efficiency μ1, the pinion rack gear efficiency μ2, the pinion rack gear. The ratio Cf is calculated from the required motor current calculation formula (2) below (step S17).

Imt = (Cf * F-2π * μ2 * Tmh * 1000) / 2π / Kt / μ1 / μ2 / Gr / 1000 (2)

Then, the tuning device 40 sets the assist map 33 based on the necessary motor current Imt calculated from the above equation (2) (step S18).

  Next, the tuning device 40 performs simulation of each compensation system in a state where the necessary motor current Imt is set in the assist map 33 in step S18, and optimizes each compensation system (step S19). The steering assist command value I output from the control unit 30 can be efficiently optimized by each compensation system optimized in step S19, the target steering torque Tmh, and the necessary motor current Imt (step S20).

  As an example, the manner in which the target steering torque Tmh is input to the steering torque Lissajous waveform diagram for the steering angle obtained by the tuning device 40 for adjustment will be described with reference to FIG.

  5 represents the steering angle of the steering wheel, and the Y-axis direction represents the magnitude of the steering torque Th. As an example, in the range of ± 25 deg in the X-axis direction at a vehicle speed of 40 km / h and a steering angular speed of 30 deg / sec, the steering torque Th is adjusted every 5 deg of the left / right steering increase / return operation of the steering handle 1. It is displayed on the device 40 and shows a state where the target steering torque Tmh is input and set. Each point represents a steering operation, and is represented by a combination of right steering R, left steering L, additional turning p, and switching back n. As an example, Rp represents “right steering addition”, Ln represents “left steering switching back”, and an example in which a set point (every 5 degrees) of the steering torque Th indicated by a circle in the drawing is input as the target steering torque Tmh. It is possible to adjust the set point (every 5 deg) on the display unit (not shown) of the tuning device 40 by freely moving the point with a mouse or the like. As described above, after inputting the target steering torque Tmh, the necessary motor current Imt calculated by the tuning device 40 is automatically calculated for each steering angle for each vehicle speed using the above equation (2). The assist map 33 is set. FIG. 6 shows a characteristic example of the required motor current Imt with respect to the target steering torque Tmh.

  FIG. 6 is a diagram of a characteristic example of the necessary motor current Imt calculated based on the target steering torque Tmh input in FIG. The tuning device 40 sets the assist map 33 with the characteristics shown in FIG. 6 for the necessary motor current Imt to be calculated.

  The necessary motor current Imt is automatically calculated by the tuning device 40 based on the rack thrust F calculated from the above equation (2) and the predicted target steering torque Tmh input in advance. The target steering torque Tmh predicted in the steering torque Lissajous waveform diagram created by the tuning device 40 may be automatically plotted in the diagram, and the required motor current Imt may be automatically calculated by the tuning device 40. Further, the steering torque Lissajous waveform diagram and the rack thrust Lissajous waveform diagram with respect to the steering angle may be a table, and the necessary motor current Imt may be calculated or set in the assist map 33 as data, or the target steering torque Tmh In this input, if the numerical value of the target steering torque is input to the tuning device 40, the required motor current Imt can be calculated, so that the same effect can be obtained.

It is a block diagram which shows the structural example of the tuning method of the electric power steering apparatus which concerns on this invention. It is a simplified diagram showing a configuration example of a tuning method for an electric power steering apparatus according to the present invention. It is a flowchart which shows the operation example which concerns on this invention. It is a figure which shows the example of the rack thrust Lissajous waveform figure which concerns on this invention. It is a figure which shows the example of the steering torque Lissajous waveform figure which concerns on this invention. It is a figure which shows the example of a characteristic of the required motor current which concerns on this invention. It is a figure which shows the structural example of a general electric power steering apparatus. It is a figure which shows the block diagram of the conventional electric power steering apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering handle 2 Column axis | shaft 3 Reduction gear 5 Pinion rack mechanism 10 Torque sensor 11 Steering angle sensor 12 Vehicle speed sensor 13 Steering angular velocity detection part 20 Motor 30 Control unit 32 Steering auxiliary command value calculating part 33 Assist map 34 Differential compensation part 35 Proportional Calculation unit 36 Integration calculation unit 40 Tuning device

Claims (5)

An electric power steering device configured to calculate a steering assist command value based on an assist map provided in the control unit and to control a motor for applying a steering assist force to the steering mechanism based on the steering assist command value. In the tuning method of the electric power steering device for tuning with a tuning device connected to the control unit,
Setting a predetermined parameter value in the tuning device;
Step 2 of inputting a target steering torque as a target to the tuning device;
A step 3 of measuring a steering torque based on a measured value of a sensor system, and estimating a rack thrust based on the measured steering torque;
Step 4 for calculating the necessary motor current based on Step 1 to Step 3;
Setting and tuning the assist map based on the required motor current; and
A method for tuning an electric power steering apparatus, comprising: The tuning method for an electric power steering apparatus according to claim 1, wherein the tuning is performed by setting a control value of each compensation system provided in the control unit to zero. The simulation is performed on the control value of each compensation system based on the necessary motor current after the tuning, and the control value of each compensation system is optimized based on the simulation. The electric power steering apparatus tuning method described. 4. The tuning device according to claim 1, wherein the tuning device generates a steering torque Lissajous waveform diagram with respect to a steering angle based on the step 3 and a rack thrust Lissajous waveform diagram with respect to the steering angle based on the step 3. A method for tuning an electric power steering apparatus according to any one of the above. 5. The electric power steering apparatus tuning method according to claim 4, wherein in step 2, the target steering torque is input to the steering torque Lissajous waveform diagram or the rack thrust Lissajous waveform diagram.

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