Abstract: A robotic system includes two joints moving a common load-bearing member along a path for positioning a load. Each joint includes a linear electric motor and a feedback loop, the latter driving the motor accurately in response to a commanded position signal, and a true position signal provided by sensor apparatus disposed alongside a track of each linear motor. Cross-coupling circuitry connects with the sensor apparatus of each joint to produce signals representing differences in positional error and in speed of the joints. The signals are injected into the feedback loops of the joints to effect a shift of power between the joints to synchronize their travel. Window comparator circuitry is employed for introduction of variable gains to the feedback loops for values of positional error and velocity which are greater than reference values in a window.

Abstract: In a serial printer a movable type character element such as a ball, disc or the like is rotated to present different type characters to the print position. The carrier for the type element is moved along the print line at a predetermined maximum velocity so long as it is possible to move the type element to the next character in time required to move the carrier from one print position to the next. If the type character set-up time is greater, the carrier is run at a slower speed and is then returned to the predetermined velocity for printing.