Apparatus for controlling steer angle of rear wheels of vehicle

Claim 2

A rear wheel steer angle controlling apparatus for automatically controlling a steer angle of rear wheels of a vehicle by controlling an actuator mechanism for generating the steer angle of the rear wheels in response to an operation of a steering wheel for generating a steer angle of front wheels of said vehicle, said apparatus comprising: a steering wheel displacement detecting means for detecting a steering wheel displacement and for generating a steering wheel displacement signal representing the steering wheel displacement; and a controlling means for controlling said actuator mechanism; characterized in that there is further provided a judging means for judging a speed of operation of said steering wheel from said steering wheel displacement signal, and said controlling means controls said actuator mechanism in accordance with a result of judgement by said judging means such that: (a) said steer angle of the rear wheels is generated in the direction counter to a direction of steer angle of the front wheels when said steering wheel is operated at a high speed; and (b) said steer angle of the rear wheels is generated in the same direction as the steer angle of the front wheels when said steering wheel is operated at a low speed.

Claim 3

A rear wheel steer angle controlling apparatus according to claim 1, wherein said controlling means controls said actuator mechanism in accordance with a result of judgement by said judging means and said steering wheel displacement signal such that: (a) a steer angle of the rear wheels corresponding to the level of said steering wheel displacement signal is formed in the direction counter to a direction of the steer angle of the front wheels when said steering wheel is operated at a high speed; and (b) a steer angle of the rear wheels corresponding to the level of said steering wheel dislacement signal is generated in the same direction as the steer angle of the front wheels when said steering wheel is operated at a low speed.

Claim 4

A rear wheel steer angle controlling apparatus according to claim 1, wherein said judging means comprises means for judging the angular frequency of said steering wheel displacement signals as said speed operation of said steering wheel.

Claim 5

A rear wheel steer angle controlling apparatus according to claim 1, wherein said judging means judges the speed of operation of said steering wheel by using a transfer function G(S) expressed by the following formula and controls said actuator mechanism in accordance with the result of judgement: where, Kd and Ke are constants which meet the condition of 0 < Kd < Ke, S is a complex frequency and T is a primary delay time constant.

Claim 6

A rear wheel steer angle controlling apparatus according to claim .1, wherein said judging means includes: a first sample hold circuit for sampling said steering wheel displacement signal at a predetermined period and holding the sampled signal thus producing a stepped voltage signal; a differential amplifier adapted for subtracting said stepped vltage signal from said steering wheel displacement signal thus outputting a saw-teeth voltage signal; a second sample hold circuit for sampling said saw-teeth voltage signal at a predetermined period and holding the sampled signal thus outputting a voltage signal; an absolute value circuit for outputting the absolute value of said voltage signal outputted from said second sample hold circuit; and a comparator circuit for comparing said absolute value outputted from said absolute value circuit with a predetermined voltage corresponding to a high steering wheel operation speed and another predetermined voltage corresponding to a low steering wheel operation speed.

Claim 7

A rear wheel steer angle controlling apparatus for automatically controlling the steer angle of rear wheels of a vehicle by controlling an actuator mechanism for generating the steer angle of rear wheels in response to an operation of a steering wheel for generating a steer angle of front wheels of .said vehicle, said apparatus comprising: a steering wheel displacement detecting means for detecting a steering wheel displacement and for generating a steering wheel displacement signal representing the steering wheel displacement; a judging means for judging a speed of operation of said steering wheel from said steering wheel displacement signal; a physical amount detecting means for detecting a physical amount related to a velocity of said vehicle and outputting a physical amount signal; and a controlling means for controlling said actuator mechanism in accordance with a result of judgement by said judging means and said physical amount signal such that: (a) when said steering wheel is operated at a high speed, a steer angle of the rear wheels is formed in the direction counter to a direction of steer angle of the front wheels such as to provide a small radius of turning circle of said vehicle when said physical amount is small and, when said physical amount is large, said steer angle of the rear wheels is determined such as to provide a greater radius of turning circle than that obtained when said physical amount is small; and (b) when said steering wheel is operated at a low speed, a steer angle of the rear wheels is formed in the same direction as the steer angle of the front wheels.

Claim 8

A rear wheel steer angle controlling apparatus for automatically controlling the steer angle of rear wheels of a vehicle by controlling an actuator mechanism for generating the steer angle of rear wheels in response to an operation of a steering wheel for generating a steer angle of front wheels of .said vehicle, said apparatus comprising: a steering wheel displacement detecting means for detecting a steering wheel displacement and for generating a steering wheel displacement signal representing the steering wheel displacement; a judging means for judging a speed of operation of said steering wheel from said steering wheel displacement signal; a physical amount detecting means for detecting a physical amount related to a velocity of said vehicle and outputting a physical amount signal; and a controlling means for controlling said actuator mechanism in accordance with a result of judgement by said judging means and said physical amount signal such that: (a) when said steering wheel is operated at a high speed, a steer angle of the rear wheels is formed in the direction counter to a direction of steer angle of the front wheels such as to provide a small radius of turning circle of said vehicle when said physical amount is small and, when said physical amount is large, said steer angle of the rear wheels is determined such as to provide a greater radius of turning circle than that obtained when said physical amount is small; and (b) when said steering wheel is operated at a low speed, a steer angle of the rear wheels is formed in the same direction as the steer angle of the front wheels.

Claim 9

A rear wheel steer angle controlling apparatus according to claim 7, wherein said controlling means controls said actuator mechanism in accordance with the result of judgement by said judging means and said physical amount signal such as to generate a steer angle 6r of the rear wheels which meets one of the following conditions: On condition of (a) { On condition of On condition of (b) On condition of where, V: vehicle running velocity Vc: predetermined value of vehicle running velocity δh: stering wheel angle f(6h): steer angle proportional to the steering wheel angle and set in the direction counter to a direction of steer angle of the front wheels when the steering wheel is operated at a high speed and in the same direction as the steer angle of the front wheels when the steering wheel is operated at a low speed f(d): physical amount related to lateral displacement of the vehicle, representing one of a yaw rate, lateral acceleration, product of the yaw rate and vehicle running velocity and product of the lateral acceleration and the vehicle running velocity f(d) C : predetermined value of physical amount related to the lateral displacement corresponding to predetermined value Vc of the vehicle running velocity Vmax: maximum vehicle running velocity f(d)max: maximum value of physical amount related to the lateral displacement of vehicle corresponding to maximum vehicle running velocity K 1 ,K 4 ,K 5 : small positive constants K 2 : positive constant for attaining coincidence of dimension K 3 : constant for preventing the denominator from becoming zero.

Claim 10

A rear wheel steer angle controlling apparatus for automatically controlling a steer angle of rear wheels of a vehicle by controlling an actuator mechanism for generating the steer angle of the rear wheels in response to an operation of a steering wheel for generating a steer angle of front wheels of said vehicle, said apparatus comprising: a steering wheel displacement detecting means for detecting a steering wheel displacement and for generating a steering wheel displacement signal representing the ' steering wheel displacement; a judging means for judging a speed of operation of said steering wheel from said steering wheel displacement signal; a physical amount detecting means for detecting a physical amount related to a lateral displacement of said vehicle and outputting a physical amount signal; and a controlling means for controlling said actuator mechanism in accordance with a result of judgement by said judging means and said physical amount signal, such that a steer angle of rear wheels is generated as the sum of: (a) a first angle proportional to said steering wheel dislacement and set in the direction counter to a direction of steer angle of the front wheels when said steering wheel is operated at a high speed and in the same direction as the steer angle of the front wheels when said steering wheel is operated at a low speed; and (2) a second angle proortional to said physical amount and set in the same direction as generation of said physical amount.

Claim 11

A rear wheel steer angle controlling apparatus for automatically controlling a steer angle of rear wheels of a vehicle by controlling an actuator mechanism for generating the steer angle of the rear wheels in response to an operation of a steering wheel for generating a steer angle of front wheels of said vehicle, said apparatus comprising: a steering wheel displacement detecting means for detecting a steering wheel displacement and for generating a steering wheel displacement signal representing the ' steering wheel displacement; a judging means for judging a speed of operation of said steering wheel from said steering wheel displacement signal; a physical amount detecting means for detecting a physical amount related to a lateral displacement of said vehicle and outputting a physical amount signal; and a controlling means for controlling said actuator mechanism in accordance with a result of judgement by said judging means and said physical amount signal, such that a steer angle of rear wheels is generated as the sum of: (a) a first angle proportional to said steering wheel dislacement and set in the direction counter to a direction of steer angle of the front wheels when said steering wheel is operated at a high speed and in the same direction as the steer angle of the front wheels when said steering wheel is operated at a low speed; and (2) a second angle proortional to said physical amount and set in the same direction as generation of said physical amount.

Claim 12

A rear wheel steer angle controlling apparatus according to claim 8, wherein said controlling means controls said actuator mechanism in accordance with the result of judgement by said judging means, said steering wheel displacement signal and said physical amount signal such as to generate a steer angle 6r of the rear wheels which meets one of the following conditions: (c) {On condition of On condition of On condition of |δr| ≦ δre (h) { On condition of |δr| > δrc where, V: vehicle running velocity Vc: predetermined value of vehicle running velocity Vmax: maximum vehicle running velocity r: yaw rate f(6h): steer angle proportional to the steering wheel displacement and set in the direction counter to a direction of steer angle of the front wheels when the steering wheel is operated at a high apeed and in the same direction as the direction of steer angle of the front wheels when the steering wheel is operated at a low speed K 1 , K 4' K 6 , K 7 , K 8 , K 9 , K 10 , K 11 : small constants K 3 : constant used for preventing dominator from becoming zero 6rc: predetermined steer angle of the rear wheels

Claim 13

A rear wheel steer angle controlling apparatus for automatically controlling a steer angle of rear wheels of a vehicle by controlling an actuator mechanism for generating the steer angle of the rear wheels in response to an operation of a steering wheel for generating a steer angle of front wheels of said vehicle, said apparatus comprising: a steering wheel displacement detecting means for detecting a steering wheel displacement and for generating a steering wheel displacement signal representing the steering wheel displacement; a judging means for judging a speed of operation of said steering wheel from said steering wheel displacement signal; a physical amount detecting means for detecting a physical amount related to a lateral displacement of said vehicle and outputting a physical amount signal; a steer angle detecting means for detecting the steer angle of the rear wheels and outputting a steer angle signal; and a controlling means for controlling said actuator mechanism in accordance with the result of judgement by said judging means, said physical amount signal and said steer angle signal, such that a steer angle of the rear wheels is generated as the sum of: (a) a first angle proportional to said steering wheel dislacement and set in the direction counter to a direction of steer angle of the front wheels when said steering wheel is operated at a high speed and in the same direction as the steer angle of the front wheels when said steering wheel is operated at a low speed; and (b) a second angle proportional to said physical amount and set in the same direction as generation of said physical amount.

Claim 14

A rear wheel steer angle controlling apparatus for automatically controlling a steer angle of rear wheels of a vehicle by controlling an actuator mechanism for generating the steer angle of the rear wheels in response to an operation of a steering wheel for generating a steer angle of front wheels of said vehicle, said apparatus comprising: a steering wheel displacement detecting means for detecting a steering wheel displacement and for generating a steering wheel displacement signal representing the steering wheel displacement; a judging means for judging a speed of operation of said steering wheel from said steering wheel displacement signal; a physical amount detecting means for detecting a physical amount related to a lateral displacement of said vehicle and outputting a physical amount signal; a steer angle detecting means for detecting the steer angle of the rear wheels and outputting a steer angle signal; and a controlling means for controlling said actuator mechanism in accordance with the result of judgement by said judging means, said physical amount signal and said steer angle signal, such that a steer angle of the rear wheels is generated as the sum of: (a) a first angle proportional to said steering wheel dislacement and set in the direction counter to a direction of steer angle of the front wheels when said steering wheel is operated at a high speed and in the same direction as the steer angle of the front wheels when said steering wheel is operated at a low speed; and (b) a second angle proportional to said physical amount and set in the same direction as generation of said physical amount.

Claim 15

A rear wheel steer angle controlling apparatus according to claim 10, wherein said sum 6r of said first and second angles is given by the following formula: where, Kd, Ke: constants which meet the condition of 0 < Kd < Ke S: complex frequency T: time constant of primary delay N: steering gear ratio 6f: steer angle of front wheels Kn: proportional constant V: vehicle running speed r: yaw rate.