The disclosure of Japanese Patent Application No. 2012-041981 filed on Feb. 28, 2012 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a vehicle control system, a steering simulating system, a steering torque application method, and a storage medium that stores a program for the steering torque application method and, more particularly, to a vehicle control system, a steering simulating system and a steering torque application method, which execute control such that a target steering torque based on driver's steering operation is achieved, and a storage medium that stores a program for the steering torque application method.
2. Description of Related Art
Conventionally, the steering torque of a steering wheel is applied when the driver controls the direction of an automobile. The steering torque balances with the sum of elements, such as the restoring force of tires, the stiffness, viscosity and friction of a steering shaft and an assist torque generated by a power steering. The assist torque generated by a power steering is originally intended to reduce a burden on driver's steering operation and to improve operability in a low vehicle speed range, and is mostly applied in the same direction as the steering torque. In recent years, there has been suggested a technique for changing an assist method on the basis of a vehicle speed, that is, for applying an assist torque in a direction opposite to a steering torque in order to improve stability in a high vehicle speed range (for example, Japanese Patent Application Publication No. 2004-175163 (JP 2004-175163 A)).
A steering feel that is good for a driver is obtained when a steering angle and a steering torque vary in accordance with a certain appropriate correlation. As described above, the magnitude of steering torque is influenced by the mechanical characteristics of tires and steering shaft; however, it is known that these mechanical characteristics vary on the basis of a vehicle speed, so a change (deterioration) in steering feel with a variation in vehicle speed is perceived as a problem. In order to solve the problem, there has been suggested a technique for controlling an assist torque generated by a power steering and, as a result, constantly maintaining a set correlation between a steering angle and a steering torque not on the basis of a vehicle speed (for example, Japanese Patent Application Publication No. 2003-285753 (JP 2003-285753 A)).
The technique described in JP 2004-175163 A and the technique described in JP 2003-285753 A are techniques for generally increasing or reducing a steering torque during steering operation. However, a variation in the steering torque in the middle of steering operation tends to be experienced by a driver. Focusing on this point, in order to improve a steering feel of a driver, there has been suggested a technique for applying an appropriate steering torque based on the tactile characteristic of a driver (for example, Japanese Patent Application Publication No. 2011-57173 (JP 2011-57173 A)). This technique introduces a concept termed a driver's resistance quantity that is obtained on the basis of a sensory quantity caused by a rate of variation in steering torque and a sensory quantity caused by a steering torque, and then sets a target steering torque, based on the correlation between a steering torque and a resistance quantity.
In order to appropriately control a turn of a vehicle, the characteristic of a steering torque and a variation in steering angle (steering velocity) during a turn in a steering system are important. However, the technique described in JP 2011-57173 A expresses a variation in steering torque in the middle of steering operation as the correlation between a steering torque and a resistance quantity, based on the tactile characteristic of the driver, and sets an appropriate steering torque from the correlation, so there is a problem that a steering velocity is not taken into consideration.
The invention provides a vehicle control system, a steering simulating system and a steering torque application method, which are able to apply an appropriate steering torque based on the sensorial characteristic of a driver on the basis of a steering velocity, and a storage medium that stores a program for the steering torque application method.
A first aspect of the invention provides a vehicle control system that includes a detector and a controller. The detector is configured to detect a steering angle of a steering wheel and a steering velocity of the steering wheel through driver's steering operation. The controller is configured to, when the steering wheel is being steered from a neutral state of the steering wheel without changing a steering direction, set a steering torque corresponding to the detected steering angle and the detected steering velocity as a target steering torque on the basis of a preset correlation at each steering velocity between a resistance quantity of the driver and one of the steering angle and the steering torque, the resistance quantity being obtained on the basis of a sensory quantity of a rate of a variation in the steering torque with respect to a variation in the steering angle and a sensory quantity of the steering torque. The controller is configured to execute control such that the set target steering torque is achieved.
According to the above first aspect, the detector detects the steering angle of the steering wheel and the steering velocity of the steering wheel through driver's steering operation. The controller, when the steering wheel is being steered from the neutral state of the steering wheel without changing the steering direction, sets a steering torque corresponding to the detected steering angle and the detected steering velocity as a target steering torque on the basis of the preset correlation at each steering velocity between a resistance quantity of the driver and one of the steering angle and the steering torque, the resistance quantity being obtained on the basis of a sensory quantity of a rate of a variation in the steering torque with respect to a variation in the steering angle and a sensory quantity of the steering torque.
The controller executes control such that the set target steering torque is achieved.
In this way, when the steering wheel is being steered from the neutral state without changing the steering direction, a target steering torque is set on the basis of the correlation at each steering velocity between a resistance quantity and one of a steering angle and a steering torque, and control is executed such that the target steering torque is achieved. By so doing, it is possible to apply an appropriate steering torque based on a driver's sensorial characteristic in response to any steering velocity.
In the above aspect of the invention, the preset correlation between the resistance quantity and one of the steering angle and the steering torque may be set such that the resistance quantity increases with an increase in the one of the steering angle and the steering torque.
In the above aspect of the invention, the controller may configured to set the steering torque corresponding to the detected steering angle and the detected steering velocity as a target steering torque on the basis of a correspondence correlation at each steering velocity between the steering angle and the steering torque, the correspondence correlation being preset on the basis of the correlation at each steering velocity between the resistance quantity and the one of the steering angle and the steering torque.
The resistance quantity may become constant when the sensory quantity of the rate of a variation in the steering torque with respect to a variation in the steering angle acceleratingly reduces with an increase in the sensory quantity of the steering torque.
The sensory quantity of the steering torque may increase together with the steering torque, and an amount of increase in the sensory quantity of the steering torque with an increase in the steering torque may change from a gradually reducing tendency to a gradually increasing tendency.
The steering torque at the time when the amount of increase with an increase in the steering torque changes from the gradually reducing tendency to the gradually increasing tendency may range from 2 to 3 Nm.
The sensory quantity of the rate of a variation in the steering torque with respect to a variation in the steering angle may be directly proportional to the logarithm of the rate of a variation in the steering torque with respect to a variation in the steering angle.
The controller may be configured to execute control such that a torque assist amount, which corresponds to the set target steering torque, or the set target steering torque is generated.
A second aspect of the invention relates to a steering simulating system. The steering simulating system includes a detector and a controller. The detector is configured to detect a steering angle of a steering wheel and a steering velocity of the steering wheel through driver's steering operation. The controller is configured to, when the steering wheel is being steered from a neutral state of the steering wheel without changing a steering direction, set a steering torque corresponding to the detected steering angle and the detected steering velocity as a target steering torque on the basis of a preset correlation at each steering velocity between a resistance quantity of the driver and one of the steering angle and the steering torque, the resistance quantity being obtained on the basis of a sensory quantity of a rate of a variation in the steering torque with respect to a variation in the steering angle and a sensory quantity of the steering torque. The controller is configured to execute control such that the set target steering torque is achieved.
A third aspect of the invention relates to a steering torque application method. The steering torque application method includes: i) detecting a steering angle of a steering wheel and a steering velocity of the steering wheel through driver's steering operation; and ii) when the steering wheel is being steered from a neutral state of the steering wheel without changing a steering direction, setting a steering torque corresponding to the detected steering angle and the detected steering velocity as a target steering torque on the basis of a preset correlation at each steering velocity between a resistance quantity of the driver and one of the steering angle and the steering torque, the resistance quantity being obtained on the basis of a sensory quantity of a rate of a variation in the steering torque with respect to a variation in the steering angle and a sensory quantity of the steering torque; and iii) executing control such that the set target steering torque is achieved.
A fourth aspect of the invention provides a computer-readable storage medium storing a program for causing a computer to execute a steering torque application method. The program causes the computer to execute the following steps i) to iii): i) detecting a steering angle of a steering wheel and a steering velocity of the steering wheel through driver's steering operation; and, ii) when the steering wheel is being steered from a neutral state of the steering wheel without changing a steering direction, setting a steering torque corresponding to the detected steering angle and the detected steering velocity as a target steering torque on the basis of a preset correlation at each steering velocity between a resistance quantity of the driver and one of the steering angle and the steering torque, the resistance quantity being obtained on the basis of a sensory quantity of a rate of a variation in the steering torque with respect to a variation in the steering angle and a sensory quantity of the steering torque; and iii) executing control such that the set target steering torque is achieved.
As described above, with the vehicle control system, steering simulating system, steering torque application method and storage medium storing the program for the steering torque application method according to the invention, when the steering wheel is being steered from the neutral state without changing the steering direction, a target steering torque is set on the basis of the correlation at each steering velocity between a resistance quantity and one of a steering angle and a steering torque, and control is executed such that the target steering torque is achieved. By so doing, it is possible to apply an appropriate steering torque based on a driver's sensorial characteristic in response to any steering velocity.
Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings.
As shown in
The computer 30 includes a CPU, a RAM and a ROM. The ROM stores programs for executing a characteristic calculation process routine (described later) and a torque control process routine (described later). The computer 30 is functionally configured as follows. As shown in
Here, the principle of the present embodiment will be described.
First, the characteristic of a general vehicle will be described. It is known that, as shown in
When the degree of decrease in stiffness has a set feature, a driver experiences a good steering feel. This is because a resistance (a sense that a resistance is applied due to the restoring force of the steering wheel toward an original position) as a result of steering operation does not unnaturally fluctuate.
The above-described characteristic that the driver experiences a good steering feel is easily understandable when taking the nonlinearity of a sense of a human into consideration. Here, sensorial characteristics against two physical quantities, that is, a steering torque and a stiffness, are key factors.
First, the correlation between a physical quantity and a sensory quantity will be described. Here, the correlation between a physical quantity and a sensory quantity for a steering torque and a stiffness will be described.
The correlation between a physical quantity of a steering torque and a sensory quantity of the steering torque is obtained by a magnitude estimation method as shown in
The correlation between a physical quantity of a stiffness and a sensory quantity of the stiffness is obtained using a method of limits as shown in
Next, the correlation between a sensory quantity of a steering torque and a sensory quantity of a stiffness in which a resistance does not unnaturally fluctuate will be described.
As a result of determining the correlation between a steering torque and a stiffness, at which the same resistance is experienced, with the use of the above-described steering simulator, it was found that the stiffness monotonously reduces against the steering torque when the sensory quantities of them are compared with each other and the sensory quantity of the steering torque is asymptotic so as to saturate at a certain constant value. As shown in
Next, resistance contour lines for each steering velocity will be described. It was found that, in the steering reaction force characteristic having the correlation between a steering torque and a stiffness, shown in
Then, through a method of correcting a steering torque on the basis of a steering velocity, the correlation between a steering torque and a stiffness, at which the same resistance is experienced even when the steering velocity is different, was obtained (
By utilizing the resistance contour lines shown in
Next, a target correlation between a steering torque and a resistance quantity in the present embodiment will be described.
For the target correlation between a steering torque and a resistance quantity, a resistance quantity that is experienced such that the resistance quantity agrees to a sensorial characteristic is determined for each steering torque in association with a steering reaction force characteristic at the time when the steering wheel is turned from the neutral position at each steering velocity with the use of the above-described steering simulator. By so doing, a target correlation at each steering velocity between a steering torque and a resistance quantity is obtained.
For example, in association with the steering reaction force characteristic at the time when the steering wheel is turned from the neutral position, as shown in
As shown in
At the neutral position of the steering wheel, both the steering angle and the steering torque are zero, so the resistance quantity at the time of start of steering operation is E0.
Thus, in the present embodiment, control for achieving a target steering torque on the basis of the correlation at each steering velocity between a steering angle and a steering torque (steering reaction force characteristic map). The correlation at each steering velocity between a steering angle and a steering torque is determined on the basis of the correlation between a steering torque and a resistance quantity. The correlation between a steering torque and a resistance quantity is determined for each steering velocity such that the resistance quantity monotonously increases with an increase in steering torque at the time when the steering wheel 16 is being steered from the neutral state without changing the steering direction.
The steering state determination unit 40 determines whether the steering wheel 16 is in the neutral state (straight ahead state) and whether the steering wheel 16 is in the steered state on the basis of the steering angle signal input from the steering angle sensor 26, and stores the result in a memory (not shown). In addition, when the steering wheel 16 is in the steered state, the steering state determination unit 40 determines in which steering direction the steering wheel 16 is steered, and stores the steering direction in the memory.
The steering state determination unit 40 determines whether the steering wheel 16 is in a one-way steered state where the steering wheel 16 is being steered from the neutral state (straight ahead state) without changing the steering direction on the basis of time-sequence data of determined results until the present state.
The steering direction of the steering wheel 16 is determined on the basis of the steering angle that is detected by the steering angle sensor 26. For example, the steering direction of the steering wheel 16 is determined on the basis of the sign of a difference between the previously input steering angle and the currently input steering angle, that is, whether the difference is positive or negative.
The steering velocity detection unit 41 calculates a temporal variation in steering angle (steering velocity) on the basis of the steering angle signal input from the steering angle sensor 26. A temporal variation in steering angle may be obtained by providing a sensor that measures a steering velocity.
The target map storage unit 42 prestores the first map for a one-way steered state at each steering velocity as shown in
The target torque setting unit 44, when it is determined that the steered state is the one-way steered state, sets the steering torque corresponding to the detected steering angle and the detected steering velocity as a target steering torque on the basis of the steering angle signal input from the steering angle sensor 26 and the first map corresponding to the steering velocity detected by the steering velocity detection unit 41. The target torque setting unit 44, when it is determined that the steered state is other than the one-way steered state, sets the steering torque corresponding to the detected steering angle as a target steering torque on the basis of the steering angle signal input from the steering angle sensor 26 and the stored second map.
The assist control unit 46 calculates the amount of increase or reduction in steering torque with respect to the target steering torque by comparing the set target steering torque with the steering torque detected by the steering torque sensor 28, and computes a command torque assist amount. In addition, the assist control unit 46 executes drive control over the electric power steering motor 24 on the basis of the computed command torque assist amount such that the steering torque that acts on the steering wheel 16 becomes the target steering torque. For drive control over the electric power steering motor 24 here, for example, proportional plus integral (PI) control based on a deviation between the target steering torque and the detected steering torque may be used.
Next, the operation of the vehicle control system 10 according to the first embodiment will be described. First, a characteristic calculation process routine shown in
Initially, in step 100, a steering velocity vs is set to zero. Subsequently, in step 101, a step size dvs of the steering velocity is set to a predetermined value. Then, in step 102, the correlation at the steering velocity vs between a steering torque and a resistance quantity, which is stored in the memory (not shown), as shown in
In step 106, a target resistance quantity ET corresponding to the steering torque T is calculated on the basis of the loaded correlation at the steering velocity vs between a steering torque and a resistance quantity. For example, when the steering torque T is zero, a target resistance quantity E0 is calculated. In subsequent step 108, the physical quantity T of the steering torque is converted to the sensory quantity of the steering torque.
In step 110, using the resistance contour line map that shows the correlation at the steering velocity vs between a sensory quantity of the steering torque and a sensory quantity of the stiffness in which the resistance quantity is a constant value, which is stored in the memory, as shown in
In step 112, the sensory quantity of the stiffness, which is calculated in step 110, is converted to a physical quantity kT of the stiffness. For example, when the steering torque T is zero, a physical quantity k0 of the stiffness is obtained.
In subsequent step 114, a combination of a steering angle qT+dT and a steering torque T+dT is calculated from the physical quantity kT of the stiffness, which is calculated in step 112, in accordance with the following mathematical expression (1), and is stored in the memory as a combination corresponding to the steering velocity vs.
For example, a combination of a steering torque and a steering angle is calculated such that the stiffness in the case where the steering torque T is close to zero is k0.
The steering angle q is updated to the steering angle qT+dT calculated with the use of the above mathematical expression (1).
In step 116, it is determined whether the steering angle and the steering torque are sufficiently large. When the steering angle and the steering torque are sufficiently large, it is determined that the correspondence correlation at the steering velocity vs in all the range between a steering torque and a steering angle is obtained, and then the process proceeds to step 120. On the other hand, when the steering angle and the steering torque are not sufficiently large, the steering torque T is increased by the step size dT in step 118, and the process returns to step 106.
In step 120, it is determined whether the steering velocity vs is sufficiently high. When the steering velocity vs is sufficiently high, it is determined that the correspondence correlation at the steering velocity vs in all the range between a steering torque and a steering angle is obtained, and then the characteristic calculation process routine ends. On the other hand, when the steering velocity vs is not sufficiently high, the steering velocity vs is increased by the step size dvs in step 122, and the process returns to step 102.
As described above, in the characteristic calculation process routine, by gradually increasing the steering torque in the step size dT, a corresponding combination of the steering torque and the steering angle is calculated, and the first map is created on the basis of the calculated correspondence correlation in all the range between a steering torque and a steering angle. For example, as shown in
Next, while the vehicle equipped with the vehicle control system 10 is travelling, a torque control process routine shown in
First, in step 130, a steering torque signal is acquired from the steering torque sensor 28, and a steering angle signal is acquired from the steering angle sensor 26. In subsequent step 131, a steering velocity is calculated on the basis of the steering angle signal acquired in step 130. In step 132, it is determined whether the steering wheel 16 is in the neutral state or the steered state on the basis of the steering angle signal acquired in step 130, and it is determined in which steering direction the steering wheel 16 is steered, and the determined results are stored in the memory (not shown).
In step 134, it is determined whether the steering wheel 16 is in the one-way steered state where the steering wheel 16 is being steered from the neutral state without changing the steering direction on the basis of time-sequence data of the results determined in step 132. When it is determined that the steering wheel 16 is in the one-way steered state, in step 136, the first map for the steering velocity calculated in step 131 is loaded from the target map storage unit 42, the steering torque corresponding to the steering angle indicated by the steering angle signal acquired in step 130 is set as a target steering torque, and then the process proceeds to step 140.
On the other hand, when it is determined in step 134 that the steering wheel 16 is not in the one-way steered state, in step 138, the second map is loaded from the target map storage unit 42, the steering torque corresponding to the steering angle indicated by the steering angle signal acquired in step 130 is set as a target steering torque, and then the process proceeds to step 140.
In step 140, a command torque assist amount is calculated on the basis of the steering torque indicated by the steering torque signal acquired in step 130 and the target steering torque set in step 136 or step 138. In step 142, the electric power steering motor 24 is subjected to drive control on the basis of the command torque assist amount calculated in step 140 such that the steering torque that acts on the steering wheel 16 becomes the target steering torque.
As described above, with the vehicle control system according to the first embodiment, when the steering wheel is being steered from the neutral state without changing the steering direction, by executing control using a set target steering torque such that the correlation at each steering velocity between a steering torque and a resistance quantity, which matches a driver's sensorial characteristic, is achieved. By so doing, it is possible to apply a steering reaction force characteristic (the degree of a variation in reaction force and stiffness during steering operation) that matches the driver's sensorial characteristic in association with a steering torque (reaction force) and a stiffness in response to any steering velocity, so the handling and stability of the vehicle and driver's steering feel improve.
Next, a vehicle control system according to a second embodiment will be described. The vehicle control system according to the second embodiment has a similar configuration to that of the first embodiment, so like reference numerals denote the same components and the description thereof is omitted.
The second embodiment differs from the first embodiment in that a first map is created on the basis of the correlation between a steering angle and a resistance quantity, which is set on the basis of a driver's sensorial characteristic.
In the second embodiment, in association with the steering reaction force characteristic at the time when the steering wheel is turned from the neutral position, as shown in
Thus, in the present embodiment, control for achieving a target steering torque on the basis of the correlation at each steering velocity between a steering angle and a steering torque (steering reaction force characteristic map), which is determined on the basis of the correlation at each steering velocity between a steering angle and a resistance quantity. The correlation at each steering velocity between a steering angle and a resistance quantity is determined such that the resistance quantity is constant in a range in which the steering angle is smaller than a predetermined value and the resistance quantity monotonously increases with an increase in steering angle in a range in which the steering angle is larger than or equal to the predetermined value at the time when the steering wheel 16 is being steered from the neutral state without changing the steering direction.
The target map storage unit 42 prestores the first map for a one-way steered state at each steering velocity as shown in
Next, a characteristic calculation process routine according to the second embodiment will be described with reference to
Initially, in step 100, a steering velocity vs is set to zero. Subsequently, in step 101, a step size dvs of the steering velocity is set to a predetermined value. Then, in step 200, the correlation at the steering velocity vs between a steering angle and a resistance quantity, which is stored in the memory (not shown), as shown in
In step 204, a resistance quantity Eq corresponding to the steering angle q is calculated on the basis of the loaded correlation at the steering velocity vs between a steering angle and a resistance quantity, and, in step 206, a target resistance quantity Eq+dq corresponding to the steering angle q+dq is calculated.
In step 208, using the resistance contour line map that shows the correlation at the steering velocity vs between a sensory quantity of the steering torque and a sensory quantity of the stiffness in which the resistance quantity is a constant value and that is stored in the memory, as shown in
In subsequent step 212, a steering torque Tq+dq is calculated from the physical quantity Tq+dq of the steering torque and the stiffness kq, found in step 208, in accordance with the following mathematical expression (2), and a combination of the steering angle q+dq and the calculated steering torque Tq+dq is stored in the memory as a combination corresponding to the steering velocity vs.
T
q+dq
=k
q
·dq+T
q (2)
The steering torque T is updated to the steering torque Tq+dq calculated with the use of the above mathematical expression (2).
In step 116, it is determined whether the steering angle q and the steering torque T are sufficiently large. When the steering angle q and the steering torque T are sufficiently large, it is determined that the correspondence correlation at the steering velocity vs in all the range between a steering torque and a steering angle is obtained, and then the process proceeds to step 120. On the other hand, when the steering angle q and the steering torque T are not sufficiently large, the steering angle q is increased by the step size dq in step 214, and the process returns to step 204.
In step 120, it is determined whether the steering velocity vs is sufficiently high. When the steering velocity vs is sufficiently high, it is determined that the correspondence correlation at the steering velocity vs in all the range between a steering torque and a steering angle is obtained, and then the characteristic calculation process routine ends. On the other hand, when the steering velocity vs is not sufficiently high, the steering velocity vs is increased by the step size dvs in step 122, and the process returns to step 200.
As described above, in the characteristic calculation process routine, by gradually increasing the steering angle in the step size dq, a corresponding combination of the steering torque and the steering angle is calculated, and the first map is created on the basis of the calculated correspondence correlation in all the range between a steering torque and a steering angle. For example, corresponding steering torques are respectively obtained for the step sizes dq of the steering angle, so the first map is generated by linearly interpolating the obtained steering torques. In addition, by gradually increasing the steering velocity dvs in the step size dvs, the first map for the steering velocity vs is generated for each step size dvs of the steering velocity. The thus generated first map for each steering velocity vs is stored in the target map storage unit 42.
The other configuration and operation of the vehicle control system according to the second embodiment are similar to those of the first embodiment, so the description is omitted.
In this way, when the steering wheel is being steered from the neutral state without changing the steering direction, by executing control using a set target steering torque such that the correlation at each steering velocity between a steering angle and a resistance quantity, which matches a driver's sensorial characteristic, is achieved. By so doing, it is possible to apply a steering reaction force characteristic (the degree of a variation in reaction force and stiffness during steering operation) that matches the driver's sensorial characteristic in association with a steering torque (reaction force) and a stiffness in response to any steering velocity, so the handling and stability of the vehicle and driver's steering feel improve.
In the above-described first and second embodiments, the description is made on the example in which, in a state other than the one-way steered state, a target steering torque is set using the second map that shows the existing known correspondence correlation between a steering angle and a steering torque; however, it is not limited to this configuration. In a state other than the one-way steered state, control may be executed such that a previously calculated command torque assist amount is held. When the steering direction is changed, control may be executed such that a command torque assist amount is reduced on the basis of the amount of return of the steering angle.
Next, a third embodiment will be described. Description will be made on an example in which the invention is applied to a vehicle control system for a steer-by-wire system. Like reference numerals denote similar components to those of the first embodiment and the description thereof is omitted.
As shown in
The computer 330, as in the case of the first embodiment, executes drive control over the reaction motor 326 such that a target steering torque set on the basis of the first map or the second map for each steering velocity is achieved. In addition, the computer 330 executes drive control over the turning motor 324 such that the steered angle of the steered wheels 12 and 14 is changed on the basis of the steering angle of the steering wheel 16, which is detected by the steering angle sensor 26.
The other configuration and operation of the vehicle control system according to the third embodiment are similar to those of the first embodiment, so the description is omitted.
In the above-described first to third embodiments, the description is made on the example in which the correspondence correlation at each steering velocity between a steering angle and a target steering torque is obtained off-line in advance; however, it is not limited to this configuration. A target steering torque corresponding to the detected steering velocity and steering angle may be obtained on-line. In this case, as shown in
Torque is caused to act on the steering wheel by the torque of the electric power steering motor or the torque of the reaction motor; instead, other than the electric power steering motor or the reaction motor, torque may be caused to act on the steering wheel with the use of another actuator, such as a variable steering gear ratio system actuator.
The description is made on the example in which the invention is applied to the vehicle control system equipped for a vehicle; instead, the invention may be applied to a steering simulating system that simulates steering operation of a vehicle. For example, it is applicable that drive simulation is carried out by, in a state where an operator is seated on a vehicle seat (not shown) provided for the steering simulating system, executing operation such that the steering wheel is steered and displaying a video image showing a visual range from a driver on the display screen of a display. In this case, the steering simulating system just needs to be configured to include the steering wheel 16, the steering shaft 18, the steering angle sensor 26, the steering torque sensor 28, the reaction motor 326 and the computer 330 in the above-described third embodiment. The computer 330 just needs to execute drive control over the reaction motor 326 and control a screen image on the display that shows a video image showing a visual range from a driver for the operator on the basis of outputs from the steering torque sensor 28 and the steering angle sensor 26.
The description is made on the example in which, in the correlation between a steering torque or steering angle and a resistance quantity, the resistance quantity is set so as to be constant in a range in which the steering torque or the steering angle is smaller than a predetermined value; however, it is not limited to this configuration. The resistance quantity just needs to be set so as to be substantially constant.
The description is made on the example in which the sensory quantity of the stiffness is defined to be directly proportional to the logarithm of the physical quantity of the stiffness; however, it is not limited to this configuration. The sensory quantity of the stiffness may be defined to be substantially directly proportional to the logarithm of the physical quantity of the stiffness.
The description is made on the example in which a target steering torque corresponding to a detected steering angle is obtained using the map that shows the correspondence correlation between a steering torque and a steering angle; however, it is not limited to this configuration. A target steering torque may be calculated from a detected steering angle in accordance with a mathematical expression that expresses the correspondence correlation between a steering torque and a steering angle.
The program according to the invention may be provided by storing the program in a storage medium.
Number | Date | Country | Kind |
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2012-041981 | Feb 2012 | JP | national |