Abstract: An improved assembly design for a portable computer. A housing has a base member with a plurality of edge guides located along the side portions and a plurality of connector sockets arranged along the inner front portion. A matching circuit board has a plurality of forwardly extending plug margins which mate with the sockets when the board is fully installed in the edge guides. The board carries the main computer system electronic components and a rigid disk memory module. The keyboard assembly, floppy disk memory and power supply are all mounted to the under surface of the housing cover member, and the display panel is mounted to the top of the cover. The design enables quick assembly of the computer, and quick removal of the circuit board for repair.

Abstract: A noise blanking circuit for eliminating evidence of noise present in an incoming alternating electrical control signal, such as a shaft encoder or tachometer signal in a servo control circuit, is disclosed. The alternating electrical signal is input to a first input of a shift register having a plurality of outputs. Clock signals having a preselected frequency are input to a second input of the shift register for digitally sampling the alternating electrical signal at the times of occurrence of the clock signals so as to produce digital samples shiftably stored in respective storage locations of the shift register, which are connected to the plurality of outputs of the shift register.

Abstract: In a rotary printer control system, a dual mode servo for controlling the velocity and position of a rotary print wheel and a print wheel carriage is normally operated at a relatively high gain value. When the servo is switched from the velocity mode to the position mode, the length of time the servo remains in the position mode is monitored and, if this exceeds a predetermined maximum time period, the gain of the servo loop is switched to a relatively low value in order to reduce oscillations of the print wheel or carriage about the HOME position. The gain reduction is accomplished by inserting a supplemental R-C network in parallel with the high gain R-C network, and the range or ratios of the relatively high gain to the relatively low gain values is from about 10 to about 30.

Abstract: A speed normalization circuit for eliminating the need to fine tune a servomechanism, such as a daisy wheel printer, after manufacture, for example, in order to compensate for speed variations caused by tolerance variations throughout the manufacturing process and evidenced by variations in the actual print wheel speed and the actual carriage speed, is disclosed. In operation, when a restore sequence is called for (power up, remote restore, cover open/resume, check/resume), the carriage is restored to the leftmost home position and is then stepped three times by an identical amount (twelve increments, 1/120 of an inch per increment). The average value of the actual carriage speed for these three movements is determined and a compensation value is selected. If the carriage speed is too slow, the nominal speed value stored in a read only memory look-up table is incremented by a fixed value (i.e.

Abstract: A digital servo system adapted for use in a dual mode coarse-fine servo system to control a movable member from a starting position to an at rest destination position. The digital servo generates a pulse train in response to varying space phase cyclic analog position signal A from an encoder coupled to the movable member. Each cycle of an analog position signal represents a small incremental amount of movement by the movable member. The pulse train provides a change in its state in time with the varying position signals. In the preferred embodiment, eight changes occur per cycle. The pulse train is integrated to provide a velocity signal which is compared with a command velocity signal.

Abstract: A dual mode servo-system providing improved motion characteristics and improved noise immunity. A relatively movable member is driven by control signals derived from actual velocity feedback signals during coarse mode operation. At the beginning of fine mode operation the actual velocity signal is sampled and used to generate a synthetic velocity signal used to control motion of the member during final deceleration, along with an actual position feedback signal, the synthetic velocity signal having a decreasing magnitude tailored to a particular application. At a predetermined maximum time period, after detent of the member, a time out circuit re-inserts the actual velocity feedback signal.Control signals for the driven member are also derived from the actual motor current by integrating the motor current, the integrated current signals being used to control motion of the member during coarse mode operation only.