IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0889165
(2004-07-13)
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등록번호 |
US-7464785
(2008-12-16)
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발명자
/ 주소 |
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출원인 / 주소 |
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인용정보 |
피인용 횟수 :
14 인용 특허 :
0 |
초록
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The invention describes vehicles where the steering effect of the driver-selected wheel angles is made identical to the steering effect of positively and independently driving the driven wheels. A method of compensating for the linear portions of the slip angles of all wheels and the linear portions
The invention describes vehicles where the steering effect of the driver-selected wheel angles is made identical to the steering effect of positively and independently driving the driven wheels. A method of compensating for the linear portions of the slip angles of all wheels and the linear portions of the longitudinal slip of the driven wheels is described where the slip angles and longitudinal slips are deduced from the forces acting on the wheels. Methods of measuring the slip angles and longitudinal slips of all wheels by means of two dummy castors are also described. Vehicles where the steering effect of the driver-selected wheel angles is made identical to the steering effect of positively and independently braking all wheels are also described. Means of applying the above principles to vehicles with either hydrostatic or mechanical drives are also described, including simplified vehicles with only two steerable wheels.
대표청구항
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The claims defining the invention are as follows: 1. A vehicle having four or more wheels of substantially the same diameter, wherein: At least two wheels are independently driveable at a specific rotational velocity about their own wheel axis and at least two wheels are independently turnable abou
The claims defining the invention are as follows: 1. A vehicle having four or more wheels of substantially the same diameter, wherein: At least two wheels are independently driveable at a specific rotational velocity about their own wheel axis and at least two wheels are independently turnable about a substantially vertical axis to specific steering angles relative to a longitudinal axis of said vehicle; said vehicle includes a first joystick pivotable by a user from a neutral position in any direction relative to said longitudinal axis so as to provide a first demand signal for movement of said vehicle in a path that is instantaneously aligned with said direction; and said vehicle includes a further control means operable by said user to provide a second demand signal specifying a radius of curvature of said path, and wherein said vehicle includes a control system that adjusts both the effective rotational velocity and the effective steering angle of each wheel so as to execute travel of said vehicle along said path in response to said first and second demand signals. 2. A vehicle according to claim 1 including four rectangularly arranged wheels, wherein said further control means comprises a part of said first joystick that is rotatable by said user about a longitudinal axis of said joystick from a neutral angular position to provide said second demand signal, and wherein said control system adjusts the rotational velocity and steering angle of each said wheel according to the following equations: description="In-line Formulae" end="lead"R/t=cot(90��θ/θmax)=(RX 2+RY2)1/2/t; description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"tan Ψ=RY/RX;description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"RY=R/(tan 2105 +1)1/2=R sin Ψ;description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"RX=R tan Ψ/(tan 2Ψ+1)1/2=R cos Ψ;description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"tan φ1=(b/2-RY)/(RX -t/2)=tan (Φ'1+α1);description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"tan φ2=(b/2-RY)/(RX +t/2)=tan (Φ'2+α2);description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"tan φ3=(b/2+RY)/(RX -t/2)=tan (Φ'3+α3);description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"tan φ4=(b/2-RY)/(RX +t/2)=tan (Φ'4+α4);description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"ω1=KdR1/RMSR=ω 1'exp[-11] where R12=(b/2-RY)2+( RX-t/2)2;description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"ω2=KdR2/RMSR=ω 2'exp[-12] where R22=(b/2-RY)2+( RX+t/2)2;description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"ω3=KdR3/RMSR=ω 3'exp[-13] where R32=(b/2-RY)2+( RX-t/2)2;description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"ω4=KdR4/RMSR=ω 4'exp[-14] where R42=(b/2-RY)2+( RY+t/2)2;description="In-line Formulae" end="tail" Where RMSR is the root mean square radius which is given by the equation: description="In-line Formulae" end="lead"RMSR=(R22+R2 2+R32+R 42)1/2/2=(RX2+R Y2+t2/4+b2/4)1/2 ;description="In-line Formulae" end="tail" and RMSWS is the root mean square wheel speed which is given by the equation: description="In-line Formulae" end="lead"RMSWS=Kd=(ω12+ω2 2+ω32+ω42)1/2 /2:description="In-line Formulae" end="tail" where ω1 and φ1 are the rotational velocity end the steering angle (clockwise positive) of the front right hand wheel respectively ω2 and φ2 a are the rotational velocity and the steering angle (clockwise positive) of the front left hand wheel respectively ω3 and φ3 are the rotational velocity end the steering angle (anticlockwise positive) of the rear right hand wheel respectively ω4 and φ4 are the rotational velocity end the steering angle (anticlockwise positive) of the rear left hand wheel respectively R is the radius of curvature of the path of the vehicle RX is the distance of the centre of curvature of the path of the vehicle to the right of the vehicle centre RY is the distance of the centre of curvature of the path of the vehicle forward of the vehicle centre b is the wheel base of the vehicle t is the track of the vehicle R1, R2, R3 and R4 are the distances of the front right hand wheel, the front left hand wheel, the rear right hand wheel and the mar left hand wheel respectively from the centre of curvature of the path of the vehicle, d is the displacement of the first joy stick, where the centre of curvature of the path of the vehicle is at right angles to the direction of displacement of the first joystick Ψ is the angle of displacement of the joystick to the left of the straight ahead position K is a suitable constant θ is the angle of rotation of the first joystick, and θmax is the maximum angle of rotation of the first joystick. 3. A vehicle according to claim 2 having four wheels and wherein said further control means includes a wheel, lever, knob or second joystick. 4. A vehicle according to claim 2, where the values of the longitudinal slip and slip angle corrected for in the control equations are deduced from the forces acting on each wheel where these forces are measured continuously by means of a triaxial load cell interposed between each wheel and the chassis of the vehicle. 5. A vehicle according to claim 4, where the value of the slip angle α' corrected for in the wheel angle control equations is given by the equation: description="In-line Formulae" end="lead"α=Fx/Cα; description="In-line Formulae" end="tail" Where Fx is the cornering force acting on the wheel and Cα is the cornering stiffness, which is given by the equation: description="In-line Formulae" end="lead"Cα=(dFx/dα) α→0=KnFzn Kn'description="In-line Formulae" end="tail" Where Kn, and Kn' and constants which characterise the tyre, and Fz is the vertical force acting on the wheel,(where n will generally) lie between 0.5 and 0.8; description="In-line Formulae" end="lead"Thus α'=Fx/(KnFzn +Kn').description="In-line Formulae" end="tail" 6. A vehicle according to claim 2, where the value of longitudinal slip corrected for in the wheel speed control equations is given by: description="In-line Formulae" end="lead"i'=Fy/Cs description="In-line Formulae" end="tail" Where Cs is the gradient of the longitudinal force Fy versus longitudinal slip curve, and is given by: description="In-line Formulae" end="lead"Cs=(dFy/di) i→0=KmFzm+K m'description="In-line Formulae" end="tail" Where km, Km' and m are parameters which characterise the tyre; description="In-line Formulae" end="lead"Thus i'='Fy/(KmFz m+Km').description="In-line Formulae" end="tail" 7. A vehicle according to claim 6, where the forces acting on each wheel are measured by means of triaxial load cells which turn with the wheels so that the cornering force Fx, the tractive force Fy and the vertical force Fz are measured directly regardless of wheel angle. 8. A vehicle according to claim 6, where the forces acting on each wheel are measured by means of triaxial load cells fixed to the chassis of the vehicle so that the longitudinal force Fy', the transverse force Fx', and Fz exerted on the chassis by each wheel are converted to the forces relative to the wheel Fx, Fy and Fz according to the equations: description="In-line Formulae" end="lead"Fy=Fy'cos φ'+Fx'sin φ';description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"Fx=Fy'cos φ'+Fy'sin φ';description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"Fz=Fz' where φ' is the actual wheel angle.description="In-line Formulae" end="tail" 9. A vehicle according to claim 2, where the centre of curvature of the path of the vehicle and its rate of rotation about this centre art measured with the aid of dummy casters located at opposite ends of the vehicle, where the effective angle of each wheel can be deduced from the said centre and the actual wheel angles, and where the effective speed of each wheel can be deduced from the said centre and the rate of rotation of the vehicle about this centre. 10. A vehicle according to claim 9, where the coordinates of the centre of curvature of the path of the vehicle Rx and Ry are calculated from the equations; description="In-line Formulae" end="lead"RX=b/(tan φR+tan φF)description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"And RY=b(tan φR-tan φF)/2(tan φR+tan φF):description="In-line Formulae" end="tail" where RX is the distance of the centre of curvature of the path of the vehicle to the right of the longitudinal axis of the vehicle, RY is the distance of the centre of curvature of the path of the vehicle forward of the transverse axis of the vehicle, b is the wheel base and φR and φF are the angles of the rear and front castors respectively, so that the effective wheel angles are given by the equations: description="In-line Formulae" end="lead"tan φ1=tan(φ1'+α1) =tan φF/(1-t(tan φR+tan φF)/2b);description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"tan φ2=tan(φ2'+α2) =tan φF/(1+t(tan φR+tan φF)/2b);description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"tan φ3=tan(φ3'+α3) =tan φR/(1-t(tan φR+tan φF)/2b);description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"tan φ4=tan(φ4'+α4) =tan φR/(1+t(tan φR+tan φF)/2b);description="In-line Formulae" end="tail" And the effective velocities of the wheels across the ground are given by the equations: description="In-line Formulae" end="lead"V1=VF(Rx-t /2)cos φF/Rxcos φ1;description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"V2=VF(Rx+t /2)cos φF/Rxcos φ2;description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"V3=VR(Rx+t /2)cos φR/Rxcos φ3;description="In-line Formulae" end="tail" description="In-line Formulae" end="lead"V4=VR(Rx-t /2)cos φR/Rxcos φ4.description="In-line Formulae" end="tail" 11. A simplified vehicle according to claim 10, where both left hand wheels are driven at the same speed and where both the right hand wheels are driven at the same speed where conflict between the wheel angle steering system and the wheel speed steering system is minimised by ensuring that the effective centre of curvature of the path of the path of the vehicle lies on the transverse axis of the vehicle, where this is achieved by detecting the actual centre of curvature by means of the front and rear castors located midway between the front and rear driven wheels respectively and adjusting the actual wheel angles until the desired centre is achieved when both the angles and speeds of the front and rear castors are identical. 12. A simplified vehicle according to claim 11, where the total angle through which the wheels can be turned is limited to (say) 90 degrees, so that a continuous variation of RX from-∞ to-(b//2+t/2) and from +(b/2+t/2) to +∞, is achievable, where a value of RX=0 can also be achieved by turning the left and right driven wheels in opposite directions and driving the wheels on one side in reverse. 13. A vehicle according to claim 6, where the actual angle of the wheels is corrected for the linear portion of the slip angle of each wheel so that the effective angle of each wheel will be closer to the ideal effective angle of each wheel so that the effective centre of curvature of the path of the vehicle is moved closer to the ideal centre selected by the driver, where the linear portion of the slip angle is estimated from measurements of the vertical and transverse forces acting on each wheel and the characteristics of the tyres used. 14. A vehicle according to claim 9, where the actual angle of the wheels is corrected for the slip angle of each wheel so that the effective angle of each wheel will be closer to the ideal effective angle of each wheel so that the effective centre of curvature of the path of the vehicle is moved closer to the ideal centre selected by the driver, where the slip angle of each wheel is deduced from the position of the centre of curvature of the path of the vehicle, where the latter is deduced from the angles and speeds of two dummy castors located at opposite ends of the vehicle. 15. A vehicle according to claims 6, where the actual speed of the wheels is corrected for the linear portion of the longitudinal slip of each wheel so that the effective speed of each wheel will be closer to the ideal effective speed of each wheel so that the effective centre of curvature of the path of the vehicle is moved closer to the ideal centre selected by the driver, where the linear portion of the longitudinal slip is estimated from measurements of the vertical and longitudinal forces acting on each wheel and the characteristics of the tyres used. 16. A vehicle according to claim 9, where the actual speed of the wheels is corrected for the longitudinal slip of each wheel so that the effective speed of each wheel will be closer to the ideal effective speed of each wheel so that the effective centre of curvature of the path of the vehicle is moved closer to the ideal centre selected by the driver, where the longitudinal slip of each wheel is deduced from the position of the centre of curvature of the path of the vehicle and the rate of rotation of the vehicle about this centre, where the latter two parameters are deduced from the angles and speeds of two dummy castors located at apposite ends of the vehicle.
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