Method and apparatus for compensating for unprogrammed changes in relative position between a machine and workpiece

An apparatus for modifying a command signal representing a predetermined position of a machine element relative to a workpiece to compensate for measurable unprogrammed changes in the relative position between said machine element and said workpiece, said machine element being controlled by a servomechanism circuit generating interrupt signals defining fixed time intervals, the apparatus comprising:

• a. means responsive to a predetermined position of the machine element relative to the workpiece for generating a start signal;
• b. means for producing feedback signals representing the sign and incremental magnitude of unprogrammed changes in the relative position between the machine element and the workpiece;
• c. means responsive to the start signal and the feedback signals for producing a first signal representing a current change in the relative position between the machine element and the workpiece with respect to a predetermined point;
• d. means responsive to an interrupt signal and the feedback signals for producing a second signal representing a change in the position of the machine element relative to the workpiece during a queuing time defined by a number of fixed time intervals;
• and
• e. means responsive to the first signal, the second signal and the command signal for producing a modified command signal, said modified command signal compensating the machine element motion for the unprogrammed changes in the relative position between the machine element and the workpiece and causing the machine element to move to the predetermined position relative to the workpiece.

A method for modifying command signals representing predetermined positions of a machine element relative to a workpiece to compensate for measurable unprogrammed changes in the relative position between said machine element and workpiece, said machine element being controlled by a servomechanism circuit generating interrupt signals defining fixed time intervals and causing command signals to be transferred to the servomechanism circuit, the method comprising the steps of:

• a. producing feedback signals representing the direction and magnitude of an unprogrammed change in the relative position between the machine element and the workpiece;
• b. initializing a command signal in response to the feedback signals as a function of the unprogrammed change in the relative position occurring up to the time of a first interrupt signal representing the most recent occurrence of an interrupt;
• c. producing, in response to the initialized command signal and the feedback signals, a modified command signal by modifying the initialized command signal as a function of the unprogrammed change in relative position occurring from the time of the first interrupt signal to the time of the second interrupt signal causing the modified command signal to be transferred to the servomechanism circuit;
• and
• d. iterating steps (b) and (c) during each fixed time interval in which an unprogrammed changed in the relative position occurs between the machine element and the workpiece occurs.

A method for modifying command signals representing predetermined positions of a machine element relative to a workpiece to compensate for measurable unprogrammed changes in the relative position between said machine element and workpiece, said machine element being controlled by a servomechanism circuit generating interrupt signals defining fixed time intervals, the method comprising the steps of:

• a. generating a start signal in response to a predetermined position of the machine element relative to the workpiece;
• b. producing feedback signals representing the direction and incremental magnitude of unprogrammed changes in the relative position between the machine element and the workpiece;
• c. producing, in response to the start signal and the feedback signals, a first signal representing a current change in the relative position between the machine element and the workpiece with respect to a predetermined point;
• d. generating, in response to the feedback signals and an interrupt signal, a second signal representing a change in the relative position between the machine element and the workpiece during a queuing time defined by a number of fixed time intervals;
• e. modifying a command signal as a function of the first signal and the second signal to produce a modified command signal, said modified command signal compensating the motion of the machine element for the unprogrammed real time changes in the relative position between the machine element and the workpiece and causing the machine element to move to the predetermined position relative to the workpiece;
• and
• f. iterating steps (b) through (e) to compensate the command signal for further unprogrammed changes in the relative position between the machine element and the workpiece.

An apparatus for causing a machine element to track a moving conveyor containing a workpiece, said machine element operating in response to a servomechanism circuit generating interrupt signals defining fixed time intervals and causing command signals to be transferred to the servomechanism circuit, said servomechanism circuit operating in response to a control system producing command signals representing successive positions of the machine relative to the workpiece along an axis of motion approximately parallel to the motion of the conveyor, the apparatus comprising:

• a. means responsive to the motion of the workpiece for generating a start signal representing the start of a tracking operation;
• b. means responsive to the start signal and the conveyor motion for producing feedback signals representing the direction and magnitude of the conveyor motion;
• c. means responsive to the start signal and the feedback signals for producing first signal representing the displacement of the conveyor relative to a predetermined point;
• d. means responsive to the interrupt signals and the feedback signals for producing a second signal representing the displacement of the conveyor during a queuing time defined by a number of fixed time intervals;
• e. means responsive to the first signal, the second signal and a command signal for generating a modified command signal representing a new position of the machine element after a subsequent queuing time;
• and
• f. means responsive to the generating means for storing the modified command signal whereby said modified command signal is transferred to the servomechanism circuit in response to an interrupt signal defining the subsequent queuing time.

An apparatus for causing a machine element to track a moving conveyor containing a workpiece, said machine element operating in response to a servomechanism circuit generating interrupt signals defining fixed time intervals and causing command signals to be transferred to the servomechanism circuit, said command signals representing coordinate values of positions of the machine element relative to a predetermined point along an axis of motion approximately parallel to the motion of the moving conveyor, the apparatus comprising:

• a. means responsive to the motion of the workpiece for generating a start signal representing the start of a tracking operation;
• b. means responsive to the start signal and the conveyor motion for producing feedback signals representing the direction and magnitude of the conveyor motion;
• c. means responsive to a command signal and the feedback signals for initializing the command signal as a function of the conveyor motion occurring from the time of occurrence of the start signal to the most recent occurrence of a first interrupt signal;
• d. means responsive to the feedback signals and the fixed time interval for modifying the initialized command signal to produce a modified command signal to compensate for conveyor motion from the time of the first interrupt signal until the occurrence of a second interrupt signal causing the transfer of the modified command signal to the servomechanism circuit;
• e. means for storing the modified command signal during the time between said first and second interrupt signals.

A method for causing a machine element to track a moving conveyor containing a workpiece, said machine element operating in response to a servomechanism circuit generating interrupt signals defining fixed time intervals and causing the command signals representing new positions of the machine element to be transferred to the servomechanism circuit, said command signals representing new positions of the machine element along an axis of motion approximately parallel to the motion of the moving conveyor, the method comprising the steps of:

• a. producing a start signal in response to the presence of the workpiece within the operating range of the machine element;
• b. producing, in response to the start signal, a first signal representing the cumulative conveyor displacement relative to a predetermined point;
• c. initializing, in response to the first signal, a command signal as a function of conveyor motion from the point of occurrence of the start signal;
• d. modifying the initialized command signal as a function of an estimate of conveyor motion occuring over a fixed time interval to produce a modified command signal;
• e. storing the modified command signal in a buffer store whereby said modified command signal is transferred to the servomechanism circuit in response to the next occurrence of an interrupt signal;
• and
• f. iterating steps (b) through (e) during each fixed time interval to cause the machine element to follow the conveyor.