Reverse direction guidance system for lift truck
First Claim
1. An improved, self-guided vehicle of the type which automatically follows an externally defined path in a forward direction and which has at least one ground engaging steerable wheel, sensor means mounted on the vehicle for generating a position error signal representative of the position of the vehicle with respect to the path, steering actuator means attached to the ground engaging steering wheel for steering the vehicle in response to a steering control signal to the steering actuator means, and steering circuit means supplied with the position error signal for generating a first steering control signal for the steering actuator means to cause the steering actuator means to automatically steer the vehicle along the external path, wherein the improvement comprises:
- sensor means for generating the position error signal relative to a virtual sense point to the rear of the vehicle to guide the vehicle when it travels in a backward direction along the path.
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Accused Products
Abstract
An automatic guidance device for a self-powered cargo moving vehicle operated by a vehicle-borne sensor which follows a buried, energized wire path and which includes sensor means mounted either between the fixed and steerable axles or in front of the fixed axle of the vehicle for guiding the vehicle when it travels in a direction such that the fixed axle precedes the sensor by effectively generating a position error signal relative to the direction of travel. In one preferred embodiment the sensor includes a pair of sensing coils whose outputs are combined to generate an error signal V=(1+K)R-KF where R and F are the difference of outputs of a pair of rear and forward sensors, respectively, and K is equal to the ratio of the distance of the rear pair of coils to the virtual sense point and the distance between the rear and forward pairs of coils.
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Citations
10 Claims
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1. An improved, self-guided vehicle of the type which automatically follows an externally defined path in a forward direction and which has at least one ground engaging steerable wheel, sensor means mounted on the vehicle for generating a position error signal representative of the position of the vehicle with respect to the path, steering actuator means attached to the ground engaging steering wheel for steering the vehicle in response to a steering control signal to the steering actuator means, and steering circuit means supplied with the position error signal for generating a first steering control signal for the steering actuator means to cause the steering actuator means to automatically steer the vehicle along the external path, wherein the improvement comprises:
sensor means for generating the position error signal relative to a virtual sense point to the rear of the vehicle to guide the vehicle when it travels in a backward direction along the path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An improved, self-guided vehicle of the type which automatically follows a path defined by a buried, energized wire and which has at least one ground engaging steerable wheel, and a pair of wheels on a fixed axle, sensor means mounted on the vehicle for generating a sensor signal representative of both the lateral position of the vehicle with respect to the wire and the inclination of direction of vehicle travel with respect to the wire, steering actuator means attached to the ground engaging steering wheel for steering the vehicle in response to a steering control signal to the steering actuator means, and steering circuit means supplied with the sensor signal for generating a first steering control signal for the steering actuator means to cause the steering actuator means to automatically steer the vehicle along the wire path, wherein the improvement comprises:
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the sensor means is mounted on the vehicle between the steerable wheel and the fixed axle and guides the vehicle along the wire path when the vehicle is traveling in a direction such that the fixed axle wheels precede the steerable wheel, the sensor means including a pair of first sensor coils and a pair of second sensor coils, the first sensor coils being mounted closest to the fixed axle wheels and each of the pairs of coils being mounted on the vehicle so as to normally straddle the wire path and each pair of the coils producing an output signal representative of the difference of the outputs of the coils of each pair, and means for generating the position error signal (V) with respect to a virtual sense point, located beyond the fixed axle wheels and in the direction of vehicle travel, according to the formula;
space="preserve" listing-type="equation">V = (1+K)A-KBwhere A = difference of outputs of first pair of sensor coils; B = difference of outputs of the second pair of sensor coils; and K = constant = ratio of distance between the first pair of sensor coils and the virtual sense point to the distance between the first and second pairs of coils.
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Specification