Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
  • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
  • B62D5/046—Controlling the motor
  • B62D5/0472—Controlling the motor for damping vibrations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
  • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
  • B62D5/046—Controlling the motor
  • B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input

Definitions

• the present invention relates to an electric power steering device for a vehicle, and more particularly to a control device for an electric power steering device.
• a control device for an electric power steering device for reducing the driver's steering load by applying a steering assist torque to a vehicle such as an automobile
• a steering assist torque to a vehicle
• Japanese Patent Application Laid-Open No. 2001-80553 As described in Japanese Patent Publication No. 5, torque that promotes steering in a direction to offset torque steer caused by the braking force difference between the left and right wheels when the vehicle travels on a so-called straddle road where the friction coefficient of the left and right road surfaces is different.
• a control device for an electric power steering device configured to control an electric power steering device based on an estimated difference in braking force between the left and right wheels so as to generate a steering reduction torque is conventionally known.
• the electric power steering device is configured to generate a torque steer reducing torque that promotes steering in a direction to cancel torque steer caused by a braking force difference between left and right wheels. Since the control is performed, the straight running performance of the vehicle and the running stability of the vehicle can be improved as compared with a case where such control is not performed.
• the torque steer caused by the braking force difference between the left and right wheels is not uniquely determined by the estimated braking force difference between the left and right wheels.
• the higher the friction coefficient of the road surface the larger the torque steer.
• an optimum torque steer reduction torque corresponding to an actual torque steer cannot be generated depending on a road surface condition.
• the braking force difference between the left and right wheels is generally determined based on the braking pressure difference between the left and right wheels.
• a detection error of a sensor that detects the braking pressure due to a detection error of a sensor that detects the braking pressure, a variation in the relationship between the braking pressure and the braking force, etc.
• the electric power steering device is unnecessarily controlled based on the braking pressure difference between the left and right wheels, and unnecessary torque Tare reduction torque may be generated.
• the problem described above is to reduce the change in vehicle behavior caused by the difference in braking force between the left and right wheels, for example, in order to reduce the change in vehicle behavior caused by the difference in braking force between the left and right wheels when the vehicle travels on a straddle road. This also occurs when the electric power steering device is controlled so as to generate a behavior change reducing torque that promotes steering in the direction of movement. Disclosure of the invention
• the present invention provides a braking force difference effect reduction torque that cancels torque steer caused by a difference in braking force between left and right wheels or promotes steering in a direction to reduce changes in vehicle behavior caused by a difference in braking force between left and right wheels.
• the present invention has been made in view of the above-described problem in controlling the electric power steering device to generate the power, and the main problem of the present invention is that in addition to the estimated difference in the power control between the left and right wheels, the road surface By taking into account the situation, it is possible to prevent the generation of unnecessary torque for reducing the influence of the braking force difference, and to generate the optimum torque for reducing the effect of the braking force difference that responds to actual torque steering and changes in behavior regardless of the road surface conditions. It is to let.
• an electric power steering apparatus for generating a braking force difference effect reducing torque that promotes steering in a direction to reduce the effect of a braking force difference between left and right wheels on a vehicle.
• a control device for an electric power steering device wherein the control device for an electric power steering device controls the torque for reducing the influence of the braking force difference according to the braking force difference between the left and right wheels and the road surface condition. Achieved.
• the torque for reducing the influence of the braking force difference is controlled in accordance with the braking force difference between the left and right wheels and the road surface condition, it is possible to respond to actual torque steer and changes in vehicle behavior regardless of the road surface condition. It is possible to generate the optimum torque for reducing the influence of the braking force difference, and this makes it possible to control the torque steering reduction torque according to only the braking force difference between the left and right wheels. In comparison, the torque for reducing the effect of the braking force difference can be appropriately controlled.
• the braking force difference effect reducing torque is a torque steer reducing torque that promotes steering in a direction to cancel torque steer caused by a difference in braking / powering between the left and right wheels. May be.
• the braking force difference effect reducing torque is a torque steer reducing torque that promotes steering in a direction that cancels torque steer caused by the braking force difference between the left and right wheels.
• the torque reduction torque is controlled according to the braking force difference and the road surface condition, so that the optimum torque steering reduction torque corresponding to the actual torque steer can be generated regardless of the road surface condition.
• the torque can be properly controlled.
• the braking force difference effect reducing torque is a behavior change reducing torque that promotes steering in a direction to reduce a change in vehicle behavior caused by a difference in braking force between the left and right wheels. It may be configured as such.
• the braking force difference effect reducing torque is a behavior change reducing torque that promotes steering in a direction to cancel torque steer caused by the braking force difference between the left and right wheels. Since the behavior change reduction torque is controlled according to the situation, the optimum behavior change reduction torque corresponding to the actual torque steer can be generated regardless of the road surface condition, and the behavior change reduction torque can be appropriately controlled. it can.
• the road surface condition may be configured to be a road surface friction coefficient.
• the road surface condition is the friction coefficient of the road surface
• the road surface condition may be determined based on the deceleration of the vehicle.
• the road surface condition is determined based on the deceleration of the vehicle, the road surface condition corresponding to the friction coefficient of the road surface can be easily determined, and the actual road surface friction coefficient can be determined regardless of the road surface friction coefficient. It is possible to generate an optimum torque for reducing the influence of the braking force difference corresponding to torque steer and behavior change.
• the magnitude of the braking force difference effect reducing torque is reduced when the deceleration of the vehicle is small compared to when the deceleration of the vehicle is large. ,.
• the difference in braking force between the left and right wheels may be determined based on at least the difference in braking force between the left and right front wheels.
• the difference in braking force between the left and right wheels that affects torque steer and changes in vehicle behavior is greater for the left and right front wheels than for the left and right rear wheels.
• the difference in the braking force between the left and right wheels is determined based on at least the difference in the braking force between the left and right front wheels. Therefore, it is possible to reliably and effectively reduce the torque steering and the change in the vehicle behavior.
• the braking force difference between the left and right wheels is the difference between the braking force difference between the left and right front wheels and the braking force difference between the left and right rear wheels, which is less weighted than the braking force difference between the left and right front wheels.
• the determination may be made based on the sum.
• the braking force difference between the left and right wheels is determined based on the sum of the braking force difference between the left and right front wheels and the braking force difference between the left and right rear wheels, which is less weighted than the braking force difference between the left and right front wheels. Therefore, it is possible to more reliably and effectively reduce the change in the torque steering and the vehicle behavior. Further, according to the present invention, in the above-described configuration, the influence of the braking force difference is reduced in accordance with the braking force difference between the left and right wheels and the road surface condition in a situation where anti-skid control is performed on at least one wheel. It may be configured to control the torque.
• the magnitude of the braking force difference effect reduction torque may be increased as the friction coefficient of the road surface on the side with the higher friction coefficient increases.
• the road surface condition is determined based on the deceleration of the vehicle in a situation where the anti-skid control is performed on at least one wheel. May be.
• the braking force difference effect reduction torque may be controlled to 0 when the deceleration of the vehicle is equal to or less than the lower limit reference value.
• the braking force difference effect reduction torque when the deceleration of the vehicle is equal to or more than the upper limit reference value, the braking force difference effect reduction torque may be controlled to zero.
• the difference in braking force between the left and right wheels may be determined based on at least the difference in braking pressure between the left and right front wheels.
• the braking force difference between the left and right wheels is the sum of the braking pressure difference between the left and right front wheels and the braking pressure difference between the left and right rear wheels, which is less weighted than the braking pressure difference between the left and right front wheels. It may be configured to be determined based on this.
• At least a basic Calculate the assist torque, calculate the target assist torque based on at least the sum of the basic assist torque and the braking force difference reduction torque, and control the electric power steering device based on the target assist torque. It may be configured as follows. Brief Description of Drawings
• FIG. 1 is a schematic configuration diagram showing one embodiment of a control device for an electric power steering device according to the present invention.
• FIG. 2 is a flowchart showing a steering assist torque control routine in the embodiment.
• FIG. 3 is a graph showing the relationship between the steering torque T s and the basic assist torque T at.
• FIG. 4 is a graph showing the relationship between the vehicle speed V and the vehicle speed coefficient Kv.
• FIG. 5 is a graph showing the relationship between the braking pressure difference ⁇ between the left and right wheels, the torque steer reducing torque T ats (thick line), and the behavior change reducing torque T avb (thin line).
• FIG. 1 is a schematic configuration diagram showing one embodiment of a control device for an electric power steering device according to the present invention.
• 10 FL and 10 FR indicate left and right front wheels which are driven wheels of the vehicle 12 respectively
• 10 RL and 10 RR indicate left and right rear wheels which are driving wheels of the vehicle 12 respectively.
• the left and right front wheels 10 FL and 10 FR which are also the steered wheels, are driven by a rack and pinion type electric power steering device 16 driven in response to the steering of the steering wheel 14 by the driver. Steered via tie rods 18 L and 18 R.
• the electric power steering device 16 is a rack coaxial electric power steering device, and is controlled by the electronic control device 20.
• the electric power steering device 16 has an electric motor 22 and, for example, a ball screw type conversion mechanism 26 that converts the rotational torque of the electric motor 22 into a reciprocating force of the rack bar 24.
• a steering assist torque for reducing the driver's steering load is generated.
• the braking force of each wheel is controlled by wheel cylinders 3 4 FR, 3 It is controlled by controlling the braking pressure of 4FL, 34RR, and 34RL.
• the hydraulic circuit 32 includes a reservoir, an oil pump, various valve devices, etc., and the braking pressure of each wheel cylinder is normally set according to the driver's depression of the brake pedal 36. It is controlled by a master cylinder 38 that is driven by an electric motor, and is controlled by an electronic control unit 40 as necessary.
• the electronic control unit 40 controls the braking pressure of the wheel in a manner known in the art to increase or decrease the braking slip, thereby reducing the braking slip.
• Perform anti-skid control (ABS control) to reduce.
• the steering shaft 42 is provided with a torque sensor 46 for detecting the steering torque Ts.
• the vehicle 12 is provided with a vehicle speed sensor 48 for detecting the vehicle speed V and a longitudinal acceleration sensor 50 for detecting the longitudinal acceleration Gx of the vehicle. Is provided.
• the torque sensor 46 detects the steering torque Ts with the left turning direction of the vehicle as positive
• the longitudinal acceleration sensor 50 detects the longitudinal acceleration Gx of the vehicle with the vehicle acceleration direction as positive.
• a signal indicating the steering torque Ts detected by the torque sensor 46 As shown, a signal indicating the steering torque Ts detected by the torque sensor 46, a signal indicating the vehicle speed V detected by the vehicle speed sensor 48, and a longitudinal acceleration Gx of the vehicle detected by the longitudinal acceleration sensor 50 are shown.
• the signal is input to the electronic control unit 20, and a signal indicating the braking pressure P i of each wheel detected by the pressure sensor 52 i is input to the electronic control unit 20 via the electronic control unit 40.
• the electronic control units 20 and 40 include, for example, a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus. It includes a microcomputer with a general configuration.
• the electronic control unit 20 calculates a basic assist torque Tab for reducing the driver's steering load based on the steering torque Ts and the vehicle speed V according to the flowchart shown in FIG. Calculate the torque steer reduction torque Tats that promotes steering in the direction that offsets torque steer caused by the braking force difference between the left and right wheels based on the pressure difference ⁇ P, and add the basic assist torque Tab and the torque steer reduction torque Tats. Based on the target assist torque T a, the assist torque by the electric power steering device 16 is controlled. In this case, the electronic control unit 20 controls the torque as the magnitude of the braking pressure difference ⁇ P between the left and right wheels increases.
• the torque steer reducing torque Tats is calculated based on the braking pressure difference ⁇ P between the left and right wheels and the deceleration Gbx of the vehicle so that the torque becomes larger.
• the electronic control unit 20 sets the vehicle deceleration Gbx equal to or smaller than the lower reference value Gbxl or equal to or smaller than the upper reference value Gbx2.
• the torque steer reducing torque Tats is set to 0, and the torque steer reducing torque Tats that promotes steering in a direction to cancel the torque steer caused by the braking force difference between the left and right wheels is not generated.
• the control by the flow chart shown in FIG. 2 is started when an ignition switch (not shown) is closed, and is repeatedly executed at predetermined time intervals until the ignition switch is opened. You.
• step 10 a signal indicating the steering angle 0 is read, and in step 20, the steering is performed such that the larger the magnitude of the steering torque Ts, the larger the basic assist torque Ta.
• the basic assist torque Tab ' is calculated from the map corresponding to the graph shown in Fig. 3, and in step 30, the vehicle speed V is adjusted so that the vehicle speed coefficient Kv decreases as the vehicle speed V increases.
• the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. 4 based on the calculated basic assist torque Tab in step 40 as the product of the vehicle speed coefficient Kv and the basic assist torque Tab '. Is calculated.
• step 50 for example, by determining whether or not the master cylinder pressure Pm is equal to or higher than the reference value, it is determined whether or not the driver is performing a braking operation, that is, whether or not the braking is being performed. If the determination is made and a negative determination is made, the process proceeds to step 90, and if a positive determination is made, the process proceeds to step 60.
• a braking pressure difference ⁇ P between the left and right wheels is calculated as a difference Pfl ⁇ Pfr between the braking pressures of the left and right front wheels.
• the braking pressure difference ⁇ P between the left and right wheels is given by Kr (eg, a positive value larger than 0 and smaller than 1 such as 0.5) as to the braking pressure difference between the left and right wheels.
• the weight may be calculated as the sum of weights obtained by reducing the weight of the braking pressure difference between the left and right front wheels with respect to the braking pressure difference between the left and right front wheels according to the following Equation 1.
• step 70 it is determined whether or not anti-skid is performed on at least one wheel. If a negative determination is made, the process proceeds to step 90. If an affirmative determination is made, the process proceeds to step 90. Go to 80.
• the lower limit reference value G bxl is a value of about 0.2 g, where g is the gravitational acceleration, and the lower limit reference value G bxl is not suitable for vehicles due to a detection error of the pressure sensor, a variation in the relationship between the braking pressure and the braking force, and the like.
• the electric power steering device is unnecessarily controlled based on the difference in braking force between the left and right wheels, and unnecessary torque steer reduction torque is generated, even though there is no torque steer or behavior change that should be suppressed. This is a reference value for preventing the operation from being performed.
• the electric power is determined based on the braking force difference between the left and right wheels in such a situation. This is a reference value for preventing the steering device from being unnecessarily controlled and generating unnecessary torque steer reduction torque.
• step 100 the larger the braking pressure difference ⁇ P between the left and right wheels, the larger the torque steer reducing torque T ats, and the higher the vehicle deceleration G bx, the larger the torque steer reducing torque T ats
• the torque steer reducing torque T ats is calculated from the map corresponding to the thick line in FIG. It is calculated.
• the target assist torque T a is calculated as the sum of the basic assist torque T ab and the torque steer reducing torque T ats, and in step 120, the target assist torque T a Is output to the electric motor 22 to reduce the steering force required by the driver and, if necessary, promote steering in the direction to offset the torque steer caused by the difference in braking force between the left and right wheels.
• the steering assist torque control is performed so as to generate the torque steer reducing torque.
• the magnitude of the steering torque T s increases as the magnitude increases, and the magnitude decreases as the vehicle speed V increases.
• the basic assist torque T ab is calculated based on the steering torque T s and the vehicle speed V.
• the torque steer reduction torque Tats is calculated based on the braking pressure difference ⁇ ⁇ between the left and right wheels and the deceleration Gbx of the vehicle, and in steps 110 and 120, the basic assist torque Tab and ⁇
• the assist torque by the electric power steering device 16 is controlled based on the target assist torque Ta which is the sum of the torque steer reducing torque Tats.
• the torque steer reducing torque Tats is such that as the magnitude of the braking pressure difference ⁇ P between the left and right wheels increases, the magnitude of the torque steer reducing torque Tats increases, and the vehicle deceleration Gbx which is an index value of the road surface friction coefficient. Is calculated based on the braking pressure difference ⁇ P between the left and right wheels and the deceleration Gbx of the vehicle so that the magnitude of the torque steer reducing torque Tats becomes larger as the tire is higher.
• the deceleration Gbx of the vehicle becomes higher as the friction coefficient of the road surface becomes higher. Therefore, the larger the coefficient of friction of the road surface is, the larger the magnitude of the torque steer caused by the braking force difference between the left and right wheels becomes, the larger the magnitude of the torque steer reduction torque Tats can be made.
• the torque steer is reduced.
• the torque steering reduction torque of the required size can be reliably generated, and the control device for the conventional electric power steering device that controls the torque steering reduction torque only in accordance with the braking force difference between the left and right wheels. In comparison, the torque steer reduction torque can be appropriately controlled.
• the torque steer reducing torque Tats is calculated such that the larger the vehicle deceleration Gbx is, the larger the torque steer reducing torque Tats becomes.
• the road surface friction coefficient becomes the vehicle deceleration. Since the determination is made based on Gbx, the road surface condition corresponding to the road surface friction coefficient can be easily determined.
• the torque steer reducing torque Tats is set to 0, and the torque steer reducing torque Tats is not generated.
• the magnitude of the braking pressure difference ⁇ P between the left and right wheels is equal to or greater than the reference value ⁇ P 0, it is possible to reliably prevent the torque steer reducing torque Tats from being generated unnecessarily.
• the torque steer reduction torque Tats is equal to the braking pressure difference ⁇ P between the left and right wheels in a situation where the anti-skid control is performed for at least one wheel.
• the deceleration G bx of the vehicle so the torque steer reducing torque T ats is controlled more accurately in accordance with the friction coefficient of the road surface than when anti-skid control is not considered. can do.
• the braking pressure difference effect ⁇ P and the deceleration of the vehicle are used as the braking force difference effect reducing torque that promotes steering in the direction that reduces the effect of the braking force difference between the left and right wheels on the vehicle.
• G bx a torque steer reducing torque T ats that promotes steering in a direction to cancel torque steer caused by a difference in braking force between the left and right wheels is calculated, but the braking force difference reducing torque is calculated as Instead of the torque steer reducing torque T ats, for example, as shown by the thin line in FIG.
• the braking force difference ⁇ P between the left and right wheels and the braking force difference between the left and right wheels are based on the deceleration G bx of the vehicle. It may be modified so as to be calculated as a behavior change reduction torque T avb that promotes steering in a direction that reduces a change in vehicle behavior.
• the braking pressure difference ⁇ P between the left and right wheels is calculated based on the braking pressure between the left and right wheels detected by the pressure sensor. It may be modified so that it is estimated based on the supply and discharge of oil to and from the wheel cylinder and is calculated based on the estimated dynamic pressure of the left and right wheels.
• the braking pressure difference ⁇ P between the left and right wheels and the deceleration G bx of the vehicle are determined.
• the torque steer reducing torque T ats is calculated based on this, the determination as to whether the vehicle deceleration G bx is smaller than the upper reference value G bx2 may be omitted.
• the reference value ⁇ P o of the braking pressure difference ⁇ P between the left and right wheels is constant regardless of the road surface friction coefficient, and thus the vehicle deceleration G bx, but the road surface friction coefficient is high.
• the vehicle deceleration Gbx may be modified so as to become smaller as the vehicle deceleration Gbx becomes higher, so as to be variably set in accordance with the road surface friction coefficient or the vehicle deceleration Gbx.
• the target assist torque T a is calculated as the sum of the basic assist torque T ab and the torque steer reducing torque T ats, but the basic assist torque T ab It is a value obtained by adding another control torque such as a damping torque for improving the convergence of the steering system in addition to the torque steer reducing torque T ats.
• the target assist torque Ta may be calculated so as to be calculated.
• the vehicle is a rear wheel drive vehicle, but the vehicle to which the present invention is applied may be a front wheel drive vehicle or a four wheel drive vehicle, and the steering assist torque may be set to an arbitrary value.
• the electric power steering device may be of any configuration known in the art as long as it can be controlled.

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Citations (4)

• 2003
  • 2003-08-26 JP JP2003301360A patent/JP4172360B2/ja not_active Expired - Fee Related
• 2004
  • 2004-08-26 CN CNB2004800015764A patent/CN100497066C/zh not_active Expired - Fee Related
  • 2004-08-26 WO PCT/JP2004/012686 patent/WO2005019011A1/ja active Application Filing

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