Abstract: A steering tiller and a steered wheel(s) of a steer-by-wire steering system of a materials handling vehicle are synchronized with one another and a virtual coupling force is exerted on the steering tiller to maintain synchronization. A motor or brake is associated with the steering tiller and the positions of the tiller and the steered wheel(s) are monitored and used to control the motor or brake to apply the virtual coupling force to the tiller. Thus, an operator of the vehicle receives feedback corresponding approximately to that experienced in a mechanically coupled steering system so that synchronism is maintained between the tiller and the steered wheel(s). In this way, if the operator attempts to oversteer or outrun the steered wheel(s) by rapid rotation of the tiller, a force proportional to the operator's action is applied to oppose that action.

Abstract: A steering tiller and a steered wheel(s) of a steer-by-wire steering system of a materials handling vehicle are synchronized with one another and a virtual coupling force is exerted on the steering tiller to maintain synchronization. A motor or brake is associated with the steering tiller and the positions of the tiller and the steered wheel(s) are monitored and used to control the motor or brake to apply the virtual coupling force to the tiller. Thus, an operator of the vehicle receives feedback corresponding approximately to that experienced in a mechanically coupled steering system so that synchronism is maintained between the tiller and the steered wheel(s). In this way, if the operator attempts to oversteer or outrun the steered wheel(s) by rapid rotation of the tiller, a force proportional to the operator's action is applied to oppose that action.

Abstract: A personnel carrying vehicle comprises a self propelled, steerable body, a telescoping mast attached to and extending upwardly from the body, and a personnel compartment attached to the mast. Two control handles are mounted within the personnel compartment, with one handle including a rocker mechanism mounted therein for pivotal movement within a generally horizontal plane to control steering and the other handle being rotated to controlling traction. Sensors ensure that the operator's hands are on both control handles and both feet are properly positioned on a floor of the operator's compartment before the vehicle can be moved or the platform raised; this ensures a four point stance, providing for operator stability and that the operator's hands and feet are within the operator's compartment anytime the vehicle is being moved or during lifting or lowering operations.

Abstract: The operational fitness of a magnetic sensor for detecting buried magnets can be tested from time to time by an electromagnet installed in proximity to the sensor. The electromagnet is a small coil of wire mounted near the sensor, such as a Hall effect device, which when energized, generates a test magnetic field. The analog output of the sensor is compared with preestablished values when the electromagnet is energized to verify the proper operation of the sensor; it is also compared with preestablished values when sensing buried magnets to confirm operation of the sensor, the strength of the buried magnet, and the alignment of the sensor with respect to the magnet. A threshold detector senses the output of the sensor to indicate when a magnetic field is detected, and the peak analog output of the sensor is stored and compared to a reference after the sensor passes the magnet.

Abstract: A lift truck control system which utilizes a distributed control network including at least a display module, a distribution module, a traction module, a brake module and a steering module. The display and steering modules each are configurable by software which controls the module and the various drivers in each module. In the preferred embodiment, the display module includes flash memory which stores application software and can be rewritten so that the performance characteristics of the modules are software configurable. The display module is connectable to a programmable cartridge which includes nonvolatile flash memory that carries application software for the display and steering modules. When connected, the cartridge downloads the particular application software which is written over the stored software in flash memory for the display and steering modules.

Abstract: A fork lift truck includes a fork level sensor located in the forks, away from the vertical mast of a lift truck for detecting the true level of the forks, and a vision system including a camera which may take several forms. In one form, a single camera is mounted in a housing which may be moved to a protected location vertically either by sliding in the carriage assembly, or by use of a parallelogram device. In another form, multiple cameras are employed where a second camera may be either mounted above the first camera in the same housing or mounted between the forks. Alternatively, the first camera may perform multiple roles by being moved vertically from a first predetermined location below the bottom of the forks to a higher elevation a second predetermined location relative to the forks.

Abstract: A lift truck control system which utilizes a distributed control network including at least a display module, a distribution module, a traction module, a brake module and a steering module. The display and steering modules each are configurable by software which controls the module and the various drivers in each module. In the preferred embodiment, the display module includes flash memory which stores application software and can be rewritten so that the performance characteristics of the modules are software configurable. The display module is connectable to a programmable cartridge which includes nonvolatile flash memory that carries application software for the display and steering modules. When connected, the cartridge downloads the particular application software which is written over the stored software in flash memory for the display and steering modules.

Abstract: A fork lift truck includes a fork level sensor located in the forks, away from the vertical mast of a lift truck for detecting the true level of the forks, and a vision system including a camera which may take several forms. In one form, a single camera is mounted in a housing which may be moved to a protected location vertically either by sliding in the carriage assembly, or by use of a parallelogram device. In another form, multiple cameras are employed where a second camera may either mounted above the first camera in the same housing or mounted between the forks. Alternatively, the first camera may perform multiple roles by being moved vertically from a first predetermined location below the bottom of the forks to a higher elevation a second predetermined location relative to the forks.

Abstract: A brake control apparatus for controlling the application of braking torque to a permanent magnet brake of the type wherein a permanent magnet creates a magnetic flux path for applying a braking torque and an electromagnet provides a continuously variable flux in opposition to the permanent magnet. Braking torque is controlled in response to a braking command signal from an operator controlled floor pedal or hand grip which varies in relation to the amount of braking desired. A control circuit responsive to the braking command signal causes braking torque to be generated in direct proportion to the amount of braking desired. The control circuit including a device for applying either direct current or pulses of current to the electromagnet, the pulse width of which varies from a minimum pulse width representing maximum braking to a maximum pulse width representing no braking. The pulses are monitored to insure proper operation.

Abstract: The operational fitness of a magnetic sensor for detecting buried magnets can be tested from time to time by an electromagnet installed in proximity to the sensor. The electromagnet is a small coil of wire mounted near the sensor, such as a Hall effect device, which when energized, generates a test magnetic field. The analog output of the sensor is compared with preestablished values when the electromagnet is energized to verify the proper operation of the sensor; it is also compared with preestablished values when sensing buried magnets to confirm operation of the sensor, the strength of the buried magnet, and the alignment of the sensor with respect to the magnet. A threshold detector senses the output of the sensor to indicate when a magnetic field is detected, and the peak analog output of the sensor is stored and compared to a reference after the sensor passes the magnet.

Abstract: A materials handling vehicle employs a two step braking process where full brakes are applied to stop the vehicle quickly when it is traveling at a fast rate, and partial braking force is applied to stop the vehicle smoothly when it is traveling slowly. The amount of the braking force is controlled by the spring force applied to the braking shoes. Whenever the vehicle is moving at or less than a predetermined speed, only the brakes on one pair of wheels, typically the load wheel brakes, that is the brakes on the wheels under the load, will be used when braking action is requested. This will permit the vehicle to stop smoothly, and not abruptly as would be the case if full braking were to be applied. If the vehicle is moving faster than the predetermined speed, then full braking force will be applied by actuating the brakes on both pairs of wheels whenever requested by the operator or by the vehicle control system.

Abstract: A digital height encoder on a turret stockpicker is used to determine platform height. A pair of fixed reference switches are provided, one to reset a digital height memory to a predetermined height value each time the switch transitions either on or off, the other at a predetermined height near the staging point of telescoping masts for initial calibration of the encoder and for verification of proper operation during normal operations. If the height measurement indicated by the encoder upon the transition of the second or verificaiton switch is not within predetermined limits, an error signal is generated and recalibration will be required. Motion of the platform is also required if the control handle is in the upward direction and the platform has not reached its predetermined upper limits.

Abstract: A variable braking force electric brake for materials handling vehicles, such as fork lift trucks, utilizes two sets of springs to urge brake pads against a rotor of a disc brake. The first set of springs provide a first level of braking force, typically one-third of the total braking force. The second set of springs provide a second level of braking force, typically two-thirds of the total. A pair of electromagnetic elements act on armatures placed between the springs and a non-magnetic brake pad support plate to selectively permit either the first set of springs alone to provide braking, the second set of springs alone, or both sets together. Initially, the current to the electromagnetic elements is strong, to insure that the associated armature is pulled toward the electromagnet, and afterwards, the current is reduced to minimize heating and power requirements.

Abstract: A materials handling vehicle, such as a turret stockpicker, is provided with control circuits and hardware to allow an operator to control the vehicle from either a standing or seated position while providing all of the safety interlocks that ensure proper operation of the vehicle. All functions of the vehicle, including raising and lowering of forks and moving the vehicle, are affected by the operator's position. The switch associated with the operator's seat indicates whether the operator is in the standing or seated position, and the control of the vehicle is appropriately modified to conform to industry standards according to the mode selected from the operator.

Abstract: A fork extension and retraction system for use with stockpickers automatically extends and retracts hydraulically extendable forks of a stockpicker when the load handler carrying the forks has moved to its extended position on the load side of the vehicle, and it also automatically retracts the forks if they have drifted from a home position before performing other fork related activities. Switches in the fork carriage assembly sense when the extendable forks are in the home position and near the home position. Other switches sense when the load handler assembly has reached its extreme positions on either side of the operator's platform. Still other switches are used to slow the traverse movement of the load handler assembly as it approaches its extreme positions, thus to cushion the shock of the load handler stopping. A control circuit senses the condition of these switches and controls the operation of both the load handle and the fork extension hydraulic system.

Abstract: A dynamic clipper is used in the guidance control circuits of a wire guided vehicle, such as a lift truck, that is guided by a wire laid in floors between storage racks into which an alternating electrical signal is provided to remove the effects of noise pulses. The wire signal is detected by sensor coils carried by the vehicle, and the amplitude of this signal is used as an indication of the distance of the vehicle to the wire. The dynamic clipper includes a first comparator having one input from the sensor coil and the other input from a reference source. All noise signals greater than the reference voltage are removed. The output is then passed to an inverter and then to a second comparator which performs the same function. Thus both the positive and negative going noise pulses greater than the reference are removed from the sensor output signal.

Abstract: An improved encoder for indicating angular position or rotation of a shaft, and particularly a digital encoder for use with materials handling vehicles, includes an index mark in an index band of the encoder that is made wider than the marks in the data tracks. Associated detecting circuitry is responsive to the wide index mark for creating a dead band around a neutral position of the encoder to permit the free movement of the encoder shaft by an angular amount determined by the width of the index band. The wide index band enlarges the tolerance permitted in the return of the shaft to its neutral position and when installing the encoder on a shaft. When an encoder having a wide index band is used with a control handle, such as in positioning devices and accelerators on materials handling vehicles, the control handle has an improved feel and response.

Abstract: The height to which the forks of a lift truck are raised is measured by an ultrasonic height measuring arrangement including a downward facing transmitting transducer, positioned on the truck platform in fixed position with respect to the forks, and a downward facing ultrasonic receiving transducer which receives ultrasonic acoustic energy waves reflected by an upward facing parabolic reflector. The receiving transducer is positioned in a casing substantially at the focal point of the parabolic reflector and is mounted by means of springs which provide vibration isolation between the casing and the transducer.

Abstract: An output distance signal related to the distance between an ultrasonic transmitting transducer and an ultrasonic receiving transducer is provided by an apparatus including a reference oscillator and a burst generator responsive to the reference oscillator which periodically generates ultrasonic burst signals. The ultrasonic transmitting transducer is responsive to the generator for providing an ultrasonic acoustic energy burst in response to each of the ultrasonic burst signals. An ultrasonic receiving transducer receives the ultrasonic acoustic energy bursts and generates detection signals in response thereto. A range window circuit is responsive to detection of an acoustic energy burst by the receiving transducer, for providing a range window signal at a time period lagging the detection signal such that a range gate will be opened for passage of the next following detection signal.

Abstract: A fork lift truck includes a fork level sensor located in the forks, away from the vertical mast of a lift truck for detecting the true level of the forks, and a vision system including a camera which may take several forms. In one form, a single camera is mounted in a housing which may be moved to a protected location vertically either by sliding in the carriage assembly, or by use of a parallelogram device. In another form, multiple cameras are employed where a second camera may be either mounted above the first camera in the same housing or mounted between the forks. Alternatively, the first camera may perform multiple roles by being moved vertically from a first predetermined location below the bottom of the forks to a higher elevation a second predetermined location relative to the forks.