Abstract: A servo controlled, proportional valve is connected in parallel with a forklift truck control valve to regulate the speed at which the fork is raised or lowered by shunting the forklift pump output to the hydraulic fluid reservoir during the raising of the fork and by restricting the return flow of fluid from the lift jack during lowering of the fork with the setting of the proportional control valve being servo controlled in response to a fork height sensor.

Abstract: The effective sensor width of a path following vehicle guidance system is enlarged by having a first gain control amplifier for amplifying the sum of the path sensor signals, a second gain control amplifier for amplifying the difference of the path sensor signals and a third amplifier, in tandem with the second amplifier for amplifying the output of the second amplifier once the second amplifier's output has peaked out. All three amplifiers are gain-controlled by the same negative feedback signal. The outputs of the first and third amplifiers are synchronously detected to provide an error signal for an electromechanical steering servo for the vehicle.

Abstract: An automatic guidance device for a self-powered cargo-moving vehicle is bolted directly over the steering column of the vehicle and is operated by a vehicle-borne sensor which follows a magnetic wire path, the guidance system having an automatic, sensor-directed mode, a manually operated power steering mode, and a manual override mode in which the guidance device is effectively disconnected and steering is undertaken by a direct mechanical linkage with the vehicle steering column.

Abstract: A power steering device for a self-powered cargo-moving vehicle has a detented steering wheel which can be shifted by the operator to select either a manually operated, power steering mode, a manual override mode in which the guidance device is effectively disconnected and steering is undertaken by a direct mechanical linkage with the vehicle steering column, and, in one embodiment, an automatic, sensor-directed mode in which the vehicle is automatically guided to follow a magnetic wire path.

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.

Abstract: An automatic guidance device for a self-powered cargo-moving vehicle is operated by a vehicle-borne sensor which follows a buried, energized wire path and includes a circuit which first switches on the automatic guidance circuit when the vehicle is heading away from the wire after it has either passed over the wire or has closely approached the wire. At all other times the vehicle is power steered through the guidance circuit under the operator's control.

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.