Digital servomechanism control system

In a multiple coordinate system for controlling movements of a device, said system including means for moving the device through a plurality of coordinates, means for providing a plurality of command signals each representing desired movement of the device along one of said coordinates, and means for providing a plurality of sensed signals each representing actual movement of the device along one of said coordinates, each of said command and sensed signals being a pulse train in which each pulse represents an incremental displacement of said device, so that the speed of movement in the corresponding coordinate is encoded in the repetition rate of the pulses, the improvement comprising:

• timing pulse generator means including a single clock pulse source, operative to produce timing signals having particular repetition rates defined by said clock pulse source, respectively, for controlling operations to be performed by said system, and a plurality of control subsystems each dedicated to regulating movement of said device under control along one of said coordinates, each of said subsystems including;
• first counter means coupled to said command signal source and said sensed signal source for producing a first positional error signal functionally related to the difference between the desired and actual positions of said device along said one coordinate, reference generator means coupled to said timing generator means and said first counter means for generating a bi-directional reference pulse signal in response to both said timing signals and said first positional error signal, said reference pulse signal having a pulse repetition rate functionally related only to the magnitude of said first positional error signal, and output means coupled to said reference generator means for applying an output signal corresponding to said reference pulse signal to said device moving means for controlling the movement of said device along one of said coordinates.

A control network for use in a system for controlling the movement of a device, said control system including means for moving said device, a source of a command signal representing desired movement of the device, a source of a sensed signal representing the actual movement of said device, said command and sensed signals being pulse trains in which each pulse represents an incremental displacement of said device, so that the speed of movement is encoded in the repetition rate of the pulses, said network comprising;

• timing pulse generator means including a single clock pulse source operative to produce timing signals having particular repetition rates defined by said clock pulse source, respectively, for controlling operations to be performed by said network, first counter means coupled to said command signal source and said sensed signal source for producing a first positional error signal functionally related to the difference between the desired and actual positions of said device, reference generator means coupled to said timing generator means and said first counter means for generating a reference pulse signal in response to both said timing signals and said first positional error signal, said reference pulse signal having a repetition rate functionally related only to the magnitude of said first positional error signal, second counter means coupled to said reference generator means and said sensed signal source for producing a second positional error signal functionally related only to the accumulated difference between the number of pulses in said reference pulse signal and said sensed signal, respectively, and drive means coupled to said second counter means for applying a signal functionally related to said second positional error signal to said device moving means for energizing said device moving means.