Lift truck control systems

In a lift truck having a steerable base frame, a mast, a hydraulic lift system operable to move a load carriage along said mast to raise and lower a payload, a traction motor system for driving said truck, and an operator control for generating a speed request signal for requesting variation of the speed of said traction motor system, the combination comprising;

• (a) means for deriving a first signal commensurate with the position of said load carriage along said mast;
• (b) means for deriving a second signal commensurate with the steering angle of said base frame;
• (c) means for deriving a third signal commensurate with the weight of the payload on said load carriage;
• (d) means for deriving a fourth signal commensurate with the direction of travel of said truck;
• and
• (e) means responsive to said first, second, third, fourth, and speed request signals for providing a speed limit signal, said speed limit signal being supplied to said traction motor system to limit the speed of said truck.

A control system for a lift truck having a fork, comprising:

• a plurality of sensors each providing a respective output voltage,
• converter means for converting the output voltages to digital signals,
• a computer, programmed with a learning program for prompting the sampling of successive ones of said sensors to provide a first group of output voltages from said sensors and a corresponding first group of digital signals,
• non-volatile storage means for storing said first group of digital signals, wherein the computer is also programmed to generate operating digital signals for controlling operation of the lift truck, in accordance with selected ones of said first group stored in said non-volatile storage means.

A method of operating a lift truck, including the steps of:

• operating a series of controls aboard said truck to generate signals indicative of operating parameters of the truck in a learning mode;
• digitizing the signals to provide a first plurality of digital signals;
• storing said first plurality of digital signals in a non-volatile memory;
• generating normal mode signals indicative of operating parameters of the truck in a normal operating mode;
• digitizing the normal mode signals while said truck is operating in said normal operating mode to provide a second plurality of digital signals;
• comparing signals of said second plurality with corresponding signals of said first plurality stored in said non-volatile memory and limiting the maximum speed of said truck in accordance with the results of said comparison.

In a lift truck having a mast, a load carriage for supporting a payload, and hydraulic power means for raising and lowering said load carriage and payload along said mast, the combination comprising;

• (a) means for sensing the weight imposed on said hydraulic power means with a given payload supported on said load carriage to provide a first data value;
• (b) means for determining the position of said load carriage along said mast to provide a second data value;
• (c) data storage means containing a group of data values each representing the weight imposed on said hydraulic power means with said load carriage at a predetermined position along said mast and with a reference payload weight on said load carriage;
• (d) means responsive to said second data value for selecting a data value from said group;
• (e) means comprising microcomputer means for combining said selected data value and said first data value to provide a third data value commensurate with the weight of the given payload on said load carriage;
• and
• (f) means responsive to said third data value for generating a speed limit signal for limiting the speed of said truck.

In a lift truck having a mast, a load carriage for supporting a payload, power means for raising and lowering said load carriage and payload along said mast, and a traction motor control system, the combination comprising:

• means for storing a first set of data values indicative of operating parameters of the truck in a learning mode;
• means for determining the height of said load carriage and payload in a normal operating mode of the truck, and for deriving a height data value representing said height;
• and
• means governed by said height data value and said first set of data values for governing said traction motor control system to limit the acceleration of the truck as a function of the height of the load carriage.

In a lift truck having a steerable base frame, a mast, a hydraulic lift system operable to move a load carriage along said mast to raise and lower a payload, a traction motor system for driving said truck, and an operator control for generating a speed request signal for requesting variation of the speed of said traction motor system, the combination comprising;

• (a) means for deriving a first signal commensurate with the position of said load carriage along said mast;
• (b) means for deriving a second signal commensurate with the steering angle of said base frame;
• (c) means for deriving a third signal commensurate with the weight of the payload on said load carriage;
• (d) means for deriving a fourth signal commensurate with the instantaneous location of the center of gravity for said truck;
• and
• (e) means responsive to said first, second, third, fourth, and speed request signals for providing a speed limit signal, said speed limit signal being connected to said traction motor system to limit the speed of said truck.