Computer control of a multi-axis radiographic instrument is utilized to prevent contact between moving surfaces of the instrument based on soft limits. The soft limits are established from a legal state table incorporating all combinations of axis movement of the equipment and relating those combinations to contacting or non-contacting states. The legal state table may be used to map efficient paths between a start and ending position and may be augmented with non-contacting transducers which may sense patient movement not incorporated into the legal state table.

A modular object handling system has a multi-level control architecture, which includes a system controller that coordinates the functions and/or operations of individual module controllers, that in turn control corresponding actuators, to provide a desired system function. The system controller performs the overall trajectory planning by taking the constraints of each of the module actuators into account. The system controller may compensate for deviations of objects from their planned trajectories by contemporaneously redetermining trajectories and trajectory envelopes to encode the various combinations of the system constraints and task requirements. The trajectory envelopes can denote regions around other trajectories to indicate control criteria of interest, such as control and collision boundaries. However, by predetermining the trajectories and trajectory envelopes, and comparing the current state of an object with the predetermined trajectory envelopes, the system controller can even more quickly determine the extent to which the state satisfies the criteria. Thus, this system simplifies on-line determinations to merely include a comparison between a particular object, a particular trajectory and the corresponding trajectory envelope. It is also desirable to predetermine trajectories and trajectory envelopes by explicitly representing the system constraints and/or task requirements. By explicitly representing the system constraints and/or task requirements, the trajectories and trajectory envelopes can be automatically predetermined when adding new constraints to an existing system, or upon creating a new system once the arrangement of module actuators is known.

An antenna arrangement on a host aircraft for generating power signals related to a direction from which a transponder reply signal is received from a threat aircraft. The arrangement includes first and second monopole antenna elements arranged along a first axis of the host aircraft, third and fourth monopole antenna elements arranged along a second axis of the host aircraft, with the second axis being orthogonal to the first axis, a first quadrature combiner coupled to the first and second monopole antenna elements for generating first and second signals from the received reply signal, and a second quadrature combiner coupled to the third and fourth monopole antenna elements for generating third and fourth signals from the received reply signal. The respective power levels of the first, second, third and fourth signals are related to the direction from which the reply signal is received from the threat aircraft.

A marine radar has a screen on which is displayed a radar image and several representations of the different control functions of the radar such as range, gain and sea clutter setting. The radar also has a key pad with three keys and a tracker ball that is connected to the radar control unit. The control unit generates a marker on the screen that is movable by the tracker ball. To change one of the control functions, the tracker ball is displaced until the marker moves into the region of the representation of the appropriate control function. The control unit then produces three boxes on the screen below the control function to indicate the different options available for that function. The user can select the desired option by pressing the appropriate one of the three keys.