JP2006062549A - Traction controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out traction control precisely. <P>SOLUTION: A motor 2 controls driving torque driving a wheel 1. A detection part 12 directly detects a longitudinal force Fx working on the wheel 1. A computing part 11a computes an actual value Tact of the driving torque based on the detected longitudinal force Fx. A setting part 11b sets a direction value Tdir for the driving torque based on a request value θa of the driving torque required from a driver. A processing part 11c compares the set direction value Tdir with the calculated actual value Tact for updating the set direction value Tdir. Then, the updated direction value Tdir is instructed to the motor 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a traction control device.

From the standpoint of improving the stability of vehicle behavior, traction control is known that limits the drive torque during acceleration or starting to prevent the wheels from slipping due to excessive drive torque being applied to the wheels. (For example, refer to Patent Document 1). Further, for example, Patent Document 2 discloses a technique for controlling the motion state of a vehicle based on the frictional force utilization rate of wheels, and traction control is cited as an example of this control technique.
JP-A-10-181564 Japanese Patent No. 3132190

  By the way, according to the conventional method, it is determined that the wheel is slipping when the wheel speed rapidly increases or when the wheel speed deviates from the speed of the vehicle body. However, since wheel slip occurs when drive torque is applied excessively, it is better to perform traction control based on drive torque than to perform traction control based on wheel speed in terms of control accuracy. preferable. Although patent document 2 mentions the point which performs traction control using a wheel friction utilization factor, the concrete content is not disclosed.

  Therefore, an object of the present invention is to accurately perform traction control.

  In order to solve this problem, the present invention provides a traction control device. The traction control device includes a control unit that controls a driving torque for driving the wheel, a detection unit that directly detects the longitudinal force acting on the wheel, and an actual value of the driving torque based on the detected longitudinal force. By comparing the calculation unit, the setting unit for setting the instruction value of the driving torque based on the required value of the driving torque requested from the driver, and the set instruction value and the calculated actual value, And a processing unit that updates the set instruction value and instructs the control unit of the updated instruction value.

  Here, in the present invention, the processing unit preferably updates the set instruction value to the calculated actual value when the calculated actual value is smaller than the set instruction value.

  Further, in the present invention, the detection unit detects the front / rear force for each of the wheels provided in the vehicle, and the calculation unit calculates an actual value based on the detected front / rear force for each wheel. The setting unit sets the indicated value for each wheel, and the processing unit calculates the calculated value for each wheel when the calculated sum of the actual values is smaller than the set indicated value. It is preferable to update the set instruction value based on the actual value.

  Further, in the present invention, each of the wheels is a detection target, and further includes a wheel speed sensor that detects a wheel speed, and the processing unit sets each of the wheels as a processing target and detects the set instruction value. Based on the speed, it is updated to a variable value between the calculated actual value and the set instruction value. The updated instruction value is calculated for the wheel whose wheel speed is slower than the other wheels. It is preferable that the tendency is closer to the indicated value. In this case, the processing unit updates the instruction value set for the first wheel with the fastest wheel speed to the calculated actual value, and sets the first wheel and the second wheel with the slowest wheel speed. The instruction values set for other wheels may be updated to an average value of the set instruction value and the calculated actual value. Further, the processing unit updates the instruction value set for the wheel whose wheel speed is equal to or higher than the first determination value to the calculated actual value, the wheel speed is smaller than the first determination value, and the first The instruction value set for the wheel larger than the determination value of 2 may be updated to an average value of the set instruction value and the calculated actual value.

  Further, in the present invention, the detection unit further detects a lateral force as an acting force acting on the wheel, and the calculation unit drives based on a resultant force of the detected longitudinal force and the detected lateral force. It is preferable to calculate the actual value of the torque.

  According to the present invention, the actual value of the driving torque is calculated based on the longitudinal force directly detected by the detection unit. As a result, it is possible to monitor the driving torque of the wheels, and it is possible to accurately determine the situation where traction control should be performed. Therefore, the accuracy of traction control can be improved.

(First embodiment)
FIG. 1 is an explanatory diagram of a vehicle to which the traction control device according to the present embodiment is applied. This vehicle is a four-wheel drive type electric vehicle driven by four wheels 1, and a motor 2 serving as a drive source is provided for each wheel. Each motor 2 is operated by electric power supplied from the battery 3, and output control of the motor 2 is performed by controlling the supplied electric power via the inverter 4. The power generated in the motor 2 is transmitted to the wheel 1 through its own output shaft 2a corresponding to the axle. When driving torque is applied to the wheel 1, the wheel 1 rotates and a driving force corresponding to the driving torque is applied to the wheel 1.

  Each of these wheels 1 is provided with a brake device 5. In the present embodiment, the brake device 5 is a known hydraulic brake device mainly composed of a caliper, a disc rotor, and a brake pad. The brake device 5 applies a braking torque to the wheel 1 and applies a braking force to the wheel 1 by pressing a brake pad against the disc rotor with a caliper. The braking force by the brake device 5 can be controlled by adjusting the hydraulic pressure supplied to a cylinder provided in the caliper.

  FIG. 2 is a block diagram showing the overall configuration of the traction control device 10. The traction control device 10 is mainly configured by a control unit 11. As the control unit 11, a microcomputer constituted by a CPU, a ROM, a RAM, an input / output interface, and the like can be used. The control unit 11 performs output control of the motor 2 based on the actual value Tact of the driving torque actually applied to each wheel 1, thereby executing traction control. Various detection signals Fx, Fy, V, and θa are input to the control unit 11 in order to perform traction control.

  FIG. 3 is an explanatory diagram of the acting force. The detector 12 detects the acting force acting on the wheel 1. In the figure, for convenience of explanation, only one block corresponding to the detection unit 12 is shown, but this detection unit 12 is provided on each of the four wheels 1. The acting force that can be detected by the detection unit 12 includes a longitudinal force Fx, a lateral force Fy, a vertical force Fz, and a brake torque Tbre. In this embodiment, the longitudinal force Fx and the lateral force Fy are important. . The longitudinal force Fx is a component force generated in the direction parallel to the wheel center plane among the friction force generated on the ground contact surface of the wheel 1, and the lateral force Fy is a component force generated in a direction perpendicular to the wheel center plane. is there. On the other hand, the vertical force Fz is a force acting in the vertical direction, that is, a so-called vertical load. The brake torque Tbre is a torque (torsional force) around the rotation axis of the wheel 1. Each detection unit 12 is mainly composed of a strain gauge and a signal processing circuit that processes an electrical signal output from the strain gauge and generates a detection signal corresponding to the acting force. Based on the knowledge that the stress generated in the output shaft (axle) 2a is proportional to the acting force, the acting force is directly detected by embedding a strain gauge in the axle 2a. The specific configuration of the detection unit 12 is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 04-331336 and 10-318862, and should be referred to if necessary.

  The wheel speed sensor 13 (not shown in FIG. 1) detects the wheel speed V by detecting the rotation state of the wheel. 3 shows only one block corresponding to the wheel speed sensor 13 as in the case of the detection unit 12, the wheel speed sensor 13 is provided in units of wheels. As the wheel speed sensor 13, for example, a magnetic sensor that detects the rotation of a gear attached to the center of the wheel 1 can be used. The accelerator opening sensor 14 is composed of a potentiometer or the like, and detects an amount of depression (accelerator opening) θa of an accelerator pedal (not shown) corresponding to a required value of driving torque by a driver.

  When the microcomputer that is the control unit 11 is functionally grasped, the control unit 11 includes a calculation unit 11a, a setting unit 11b, and a processing unit 11c. The computing unit 11a calculates an actual value Tact of driving torque for driving the wheel 1 based on at least the longitudinal force Fx. The setting unit 11b sets a drive torque instruction value Tdir based on the accelerator opening degree θa. The processing unit 11c updates the set instruction value Tdir by comparing the set instruction value Tdir with the calculated actual value Tact. The updated instruction value Tdir is output to the motor 2 (more precisely, the inverter 4) that controls the driving torque of each wheel 1.

  FIG. 4 is a flowchart showing a traction control routine according to the present embodiment. The routine shown in this flowchart is called at predetermined intervals and executed by the control unit 11. First, an outline of a control routine according to the traction control method will be described. In this control method, as the first step, the longitudinal force acting on the wheel is directly detected, and as the second step, the actual value of the driving torque for driving the wheel is calculated based on the detected longitudinal force. Is done. Next, as a third step, a drive torque instruction value is set based on the drive torque request value requested by the driver. As a fourth step, the set instruction value and the calculated actual value are Is set, the set instruction value is updated. As a fifth step, the drive torque is controlled based on the updated instruction value.

  In this traction control method, the fourth step is preferably a step of updating the set instruction value to the calculated actual value when the calculated actual value is smaller than the set instruction value. Further, the first step may be a step of detecting the longitudinal force with each of the wheels provided in the vehicle as a detection target. In this case, the second step is a step of calculating an actual value based on each of the detected longitudinal forces for each wheel, and the third step is a step of setting an instruction value for each wheel. Yes, the fourth step is a step of updating the set instruction value based on the calculated actual value for each wheel when the calculated sum of the actual values is smaller than the set instruction value. It is desirable that

  Hereinafter, a specific control routine of the traction control method will be described. First, in step 1, various detection values are read. The detection values read in step 1 include the acting force (specifically, the longitudinal force Fx and the lateral force Fy) in each wheel 1, the wheel speed V in each wheel 1, and the accelerator opening θa. .

  In step 2, it is determined whether or not the accelerator opening θa is larger than a determination value θth (θth≈0%). The traction control is control at the time of driving the vehicle, and it is assumed that the accelerator pedal is depressed by the driver. Therefore, whether or not the accelerator pedal is being depressed by the driver is determined based on the determination in step 2. If a negative determination is made in step 2, that is, if the accelerator opening θa is equal to or smaller than the determination value θth, the processing after step 3 is skipped and the routine is exited. On the other hand, if an affirmative determination is made in step 2, that is, if the accelerator opening θa is larger than the determination value θth, the process proceeds to step 3.

  In step 3, an instruction value Tdir for the driving torque in each wheel 1 is set. First, the vehicle speed (hereinafter simply referred to as “vehicle speed”) Vb is calculated by calculating the average value of the wheel speeds V of the wheels 1. Next, based on the accelerator opening θa and the vehicle speed Vb, an instruction value Tdtot of the drive torque for the entire wheel is calculated. The relationship between the two variables θa, v and the instruction value Tdtot is set in advance by a map or a function expression created through simulation or experiment. For example, when a map is used, the relationship among the accelerator opening θa, the vehicle speed v, and the instruction value Tdtot is stored in advance in a ROM in the microcomputer. The instruction value Tdtot calculated using the map indicates the driving torque required for the entire vehicle, that is, the total sum of the driving torque in the four wheels. Therefore, the instruction value Tdir of the driving torque in each wheel 1 is set to a value according to the distribution ratio of the driving torque to each wheel 1 with reference to the map-based instruction value Tdtot. This distribution ratio is fixedly set in advance, or is variably set according to the motion state of the vehicle. For example, when the drive torque is equally distributed to each of the four wheels, the instruction value Tdir of each wheel 1 is set to a value obtained by adding “0.25” to the map-based instruction value Tdir.

  In step 4, the actual value Tact of the drive torque actually applied to the wheel 1 is calculated for each of the wheels 1. Specifically, first, based on the longitudinal force Fx and the lateral force Fy, the resultant force Fx, Fy (hereinafter referred to as “wheel resultant force”) F is calculated. This wheel resultant force F corresponds to the driving force actually applied to the wheel 1. Then, the actual value Tact of the drive torque actually applied to the wheel 1 is calculated by integrating the calculated wheel resultant force F and the wheel radius r.

  In step 5, the actual drive torque value Tact is compared with the required drive torque value Tdir. In this step 5, whether or not the total value Tatot of the actual values Tact in each wheel is smaller than the total value Tdtot of the required values Tdir in each wheel, because all wheels 1 that are driving wheels are processed. Is judged. If the determination in step 5 is affirmative, that is, if the total sum Tdtot of the requested values Tdir is larger than the total sum Tatot of the actual values Tact (Tatot <Tdtot), the process proceeds to step 6. On the other hand, if a negative determination is made in step 5, that is, if the sum Tdtot of the requested values Tdir is less than or equal to the sum Tatot of the actual values Tact (Tatot ≧ Tdtot), step 6 is skipped and the process proceeds to step 7.

  In step 6, the instruction value Tdir is updated for each of the wheels 1 as a processing target. In this update process, the drive torque instruction value Tdir is updated based on the wheel speed V of each wheel 1. Specifically, the indicated value Tdir of the wheel 1 having the fastest wheel speed V is changed to the actual value Tact of the drive torque (Tdir ← Tact). Next, for the wheel 1 with the slowest wheel speed V, the command value Tdir is updated to the previously calculated drive torque command value Tdir (that is, the value is maintained as it is (Tdir ← Tdir)). . On the other hand, the other wheel 1 except the wheel 1 described above has its instruction value Tdir changed to the average value of the actual value Tact of the drive torque and the instruction value Tdir (Tdir ← (Tdir + Tact) / 2).

  In step 7, a control signal corresponding to the set instruction value Tdir is output to the corresponding inverter 4 of the motor 2, and the routine is exited. As a result, the output of each motor 2 is adjusted so that the driving torque according to the updated instruction value Tdir is applied to the wheel 1.

  As described above, according to the present embodiment, the actual value Tact of the driving torque applied to the wheel 1 is calculated based on the longitudinal force Fx detected by the detection unit 12. When the wheel 1 is driven in a normal traveling state, the actual value Tact corresponds to the drive torque instruction value Tdir according to the driver's request. However, on a road surface with a low coefficient of friction, the wheel 1 slips in a situation of starting or acceleration. That is, the driving force is saturated, and the indicated value Tdir tends to be larger than the actual value Tact in the wheel 1.

  Therefore, in the present embodiment, when the instruction value Tdir is set, the actual value Tact and the instruction value Tdir are compared, and based on the comparison result, the instruction value Tdir is updated and output control of the motor 2 is performed. Is done. Thereby, in the case where the driving force is excessively given by the instruction value Tdir, the occurrence of slip can be suppressed by limiting the driving torque. Therefore, the lateral force of the wheels is ensured, and the stability of the vehicle can be improved. In the present embodiment, since the force acting on the wheel 1 is directly detected, the driving torque can be calculated with high accuracy. Thereby, since the situation where traction control is necessary can be determined with high accuracy, the accuracy of traction control can be improved. In the present embodiment, the update of the instruction value Tdir is not only actively changing the value as in the case shown in step 6 described above, but also in the case of skipping this step 6 or the like. , Including not changing the value (that is, updating with the same value).

  In a four-wheel drive vehicle, for example, when the difference between the front wheel output and the rear wheel output is increased, the wheel 1 having a small output is pulled by the other wheel 1, so that the longitudinal force Fx does not easily act on the wheel 1. This happens. However, in this embodiment, based on the detected wheel speed V, the instruction value Tdir is updated to a variable value between the actual value Tact and the instruction value Tdir. In this case, the updated instruction value Tdir tends to be closer to the calculated instruction value Tdir as the wheel 1 has a wheel speed V slower than the other wheels 1. That is, as the wheel 1 has a slower wheel speed V than the other wheels 1, the limitation on rotational torque with respect to the initially set instruction value Tdir is relaxed. As a result, it is possible to reduce the occurrence of an output difference between the wheels, so that the front / rear force Fx acts effectively on each wheel 1 and the four-wheel drive characteristics can be effectively exhibited.

  In order to suppress the output difference between the wheels, for example, the traction control is not performed below the preset minimum limit torque, or the instruction value Tdir is updated so that the torque distribution of the front and rear wheels 1 is within a certain range. Limits may be provided. Further, when the lateral force Fy is sufficiently larger than the longitudinal force Fx, that is, when the lateral force Fy is secured to some extent, the torque limitation may be relaxed. However, the present invention is not limited to such control in consideration of the entire four wheels. It is only necessary to focus on the individual wheels 1 and limit the driving torque in the comparison between the instruction value Tdir and the actual value Tact. Specifically, when the actual value Tact is smaller than the instruction value Tdir, the instruction value Tdir may be changed to the actual value Tact (update process), and the output control of the motor 2 may be performed based on this value.

  In the present embodiment, when the actual value Tact of the driving torque is calculated, the driving force (wheel resultant force F) is calculated as a resultant force of the longitudinal force Fx and the lateral force Fy. However, the present invention is not limited to this, and only the longitudinal force Fx may be handled as the driving force. Even with this method, the same effects as those of the above-described embodiment can be obtained.

  Further, in the above-described embodiment, the instruction value Tdir is updated based on the relative comparison of the wheel speeds V in the respective wheels 1. However, the present invention is not limited to this. Not. For example, two determination values Vth1 and Vth2 having different values may be used (Vth1> Vth2), and the instruction value Tdir of each wheel 1 may be updated by comparison with these determination values Vth1 and Vth2. Specifically, for the wheel 1 whose wheel speed V is equal to or higher than the determination value Vth1, the indicated value Tdir is updated to the actual value Tact of the driving torque (Tdir ← Tact), and the wheel 1 whose wheel speed V is equal to or lower than the determination value Vth2 The instruction value Tdir is updated to the set instruction value Tdir (Tdir ← Tdir). On the other hand, for the wheel 1 in which the wheel speed V is larger than the determination value Vth2 and smaller than the determination value Vth1, the instruction value Tdir is changed to an average value of the actual value Tact of the drive torque and the instruction value Tdir. (Tdir ← (Tdir + Tact) / 2).

  Note that the rotational torque applied to the wheel 1 is controlled by controlling the output of the motor 2, and thus the drive torque is limited. However, the rotational torque can be limited by adding the brake torque Tbre. Good. Specifically, based on the knowledge that the detection unit 12 can detect the brake torque Tbre, the value obtained by subtracting the brake torque Tbre from the actual value Tact matches the indicated value Tdir. The brake device 5 is controlled. Moreover, in this embodiment, traction control was demonstrated using the electric vehicle which provided the motor 2 in the wheel unit. However, the present invention can also be applied to an electric vehicle that uses a power distribution device that distributes power to each wheel 1 and drives a plurality of wheels 1 by a single motor 2. In this case, the drive source is not limited to the motor 2, and an engine can also be used. In addition, when distributing the motive power with respect to each wheel 1 with a power distribution device, since it is difficult to adjust a driving torque with a single wheel, it is preferable to limit the driving torque with the brake device 5 as described above. Further, in such an automobile, when the saturation of the driving force is determined by comparing the actual value Tact and the instruction value Tdir, the driving torque is limited as a whole wheel by reducing the output of the motor 2 or the engine. This technique is also effective. That is, in the present invention, various members such as the motor 2, the brake device 5, and the engine can be used as means for controlling the driving torque.

  In the present embodiment, the detection unit 12 is configured to detect the component force acting in three directions and the brake torque Tbre as the acting force, but the present invention is not limited to this and is necessary. It is sufficient that the acting force acting in the component force direction (in this embodiment, the longitudinal force Fx and the lateral force Fy) can be detected. The detection unit 12 may be a six-component force meter that detects six-component force including a moment around the three-component force direction. Even in such a configuration, there is no problem as a matter of course, since at least the required acting force can be detected. In addition, about the method of detecting the six component force which acts on the wheel 1, since it is disclosed by Unexamined-Japanese-Patent No. 2002-039744 and Unexamined-Japanese-Patent No. 2002-022579, please refer if necessary.

  Moreover, although this embodiment demonstrated the case where the detection part 12 was embed | buried under the axle shaft 2a, this invention is not limited to this, Other variations can also be considered. From the viewpoint of detecting the acting force, for example, the detection unit 12 may be provided on a member that holds the wheel 1, such as a hub or a hub carrier. The method of providing the detection unit 12 in the hub is disclosed in Japanese Patent Application Laid-Open No. 2003-104139, so refer to it if necessary.

Explanatory drawing of the vehicle to which the traction control device concerning this embodiment was applied Block diagram of traction control device Illustration of acting force The flowchart which shows the traction control routine concerning this embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wheel 2 Motor 2a Output shaft 3 Battery 4 Inverter 5 Brake device 10 Traction control device 11 Control unit 11a Calculation part 11b Setting part 11c Processing part 12 Detection part 13 Wheel speed sensor 14 Accelerator opening degree sensor

Claims (7)

In the traction control device,
A control unit for controlling a driving torque for driving the wheel;
A detection unit that directly detects the longitudinal force acting on the wheel;
An arithmetic unit that calculates an actual value of the driving torque based on the detected longitudinal force;
A setting unit configured to set an instruction value of the drive torque based on a request value of the drive torque requested from a driver;
A processor that updates the set instruction value by comparing the set instruction value with the calculated actual value, and that instructs the control unit to provide the updated instruction value. A traction control device comprising:   2. The processing unit according to claim 1, wherein when the calculated actual value is smaller than the set instruction value, the processing unit updates the set instruction value to the calculated actual value. Traction control device. The detection unit detects the front-rear force with each of the wheels provided in a vehicle as a detection target,
The calculation unit calculates the actual value based on the detected longitudinal force for each wheel,
The setting unit sets the instruction value for each wheel,
The processing unit updates the set instruction value based on the calculated actual value for each wheel when the calculated total sum of the actual values is smaller than the set instruction value total. The traction control device according to claim 1 or 2, characterized in that: With each of the wheels as a detection target, the vehicle further includes a wheel speed sensor that detects a wheel speed,
The processing unit sets each of the wheels as a processing target, and changes the set instruction value between the calculated actual value and the set instruction value based on the detected wheel speed. Updated to value,
4. The traction control device according to claim 3, wherein the updated instruction value tends to be closer to the calculated instruction value as the wheel speed of the wheel is slower than other wheels.   The processing unit updates the instruction value set to the first wheel with the fastest wheel speed to the calculated actual value, and the first wheel and the second wheel speed with the slowest wheel speed. 5. The traction control according to claim 4, wherein the instruction value set for the wheels other than the wheel is updated to an average value of the set instruction value and the calculated actual value. apparatus.   The processing unit updates the instruction value set for the wheel at which the wheel speed is equal to or higher than a first determination value to the calculated actual value, and the wheel speed is higher than the first determination value. The instruction value set for the wheel that is smaller and equal to or larger than the second determination value that is smaller than the first determination value is an average of the set instruction value and the calculated actual value. The traction control device according to claim 4, wherein the traction control device is updated to a value. The detection unit further detects lateral force as acting force acting on the wheel,
The said calculating part calculates the actual value of the said driving torque based on the resultant force of the said detected longitudinal force and the detected lateral force, It is described in any one of Claim 1 to 6 characterized by the above-mentioned. Traction control device.

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