Boom control system

DETAILED DESCRIPTION In accordance with the present invention, a control system for a boom, arm or other member, the length and angle with respect to a reference plane of which are adjustable by means of actuators permits the end of the boom to be moved in a chosen straight line in a simple and effective manner.
The control system includes controlling means for operating the actuators in either of two modes of operation.
The first mode of operation is the conventional polar coordinate mode of operation in which independent control over each actuator is exercised.
The second mode of operation, also referred to as orthographic coordinate mode of operation, comprises synchronized operation of the actuators so that the end of the member may be moved in a straight line.
Means are coupled to the controlling means for manually selecting one of the two modes of operation.
In a preferred form of the invention, the controlling means includes a pair of parallel-connected valves for controlling each actuator.
A first valve of each pair comprises a manual hydraulic valve.
One or both of these manual valves can be manipulated in the first mode of operation to exercise independent control over each actuator.
A second valve of each pair comprises an electrohydraulic valve which is controlled by a processor, such as a microcomputer.
The processor receives input from sensors representing the position of the boom or arm and an input from a mode switch.
When the mode switch is moved to a particular position, the actuators are operated in the orthographic coordinate mode of operation whereby manipulation of one of the manual valves to change either the boom extension or angle causes the processor to operate the electrohydraulic valve associated with the other actuator so that straight line movement of the end of the member is effected.
The processor of the control system may also include means operative in the orthographic coordinate mode of operation for preventing a condition wherein one of the electrohydraulic valves cannot provide sufficient flow to an actuator to effect the desired straight line movement