Abstract: A controller operable in a normal mode of operation to control an output device in response to a sensed condition includes means for detecting a fault in the controller or output device. Means are responsive to the fault detecting means for controlling the output device in a failsafe mode of operation wherein the output device is safely operated without regard to the sensed condition when a fault is detected. Means responsive to the fault detecting means causes a return to the normal mode of operation only if the existence of the fault can be detected while in the failsafe mode and the fault ceases to exist during such time.

Abstract: This invention relates to a motor control system for a brushless DC motor having an inverter responsively coupled to the motor control system and in power transmitting relationship to the motor. The motor control system includes a motor rotor speed detecting unit that provides a pulsed waveform signal proportional to rotor speed. This pulsed waveform signal is delivered to the inverter to thereby cause an inverter fundamental current waveform output to the motor to be switched at a rate proportional to said rotor speed. In addition, the fundamental current waveform is also pulse width modulated at a rate proportional to the rotor speed.A fundamental current waveform phase advance circuit is controllingly coupled to the inverter.

Abstract: An auxiliary power unit for an aircraft drives an electrical generator and an air compressor. The auxiliary power unit is primarily intended for operation with the aircraft on the ground when other aircraft power systems are shut down. The auxiliary power unit may, however, be used in an emergency to supplement the main aircraft generating system, with the aircraft airborne. When the auxiliary power unit generator is used in conjunction with the aircraft generating system, inlet air to the compressor is controlled to vary the compressor load on the power unit to minimize power unit speed changes and electrical frequency transients.

Abstract: A surge control system for controlling and preventing a surge condition and a method of controlling surge in a fixed or variable speed compressor or a compressor having a variable geometry which provides air to a pneumatic load. A transducer provides a signal proportional to the outlet pressure of the air from the compressor. The signal is differentiated with respect to time and if a surge condition is ensuing, the absolute value of the differentiated signal is greater than a reference. When the differentiated signal is greater than the reference, a portion of the air supplied to the load is vented to reduce the outlet pressure. A reduction in the outlet pressure alleviates the ensuing surge condition and the absolute value of the differentiated signal decreases, causing the venting valve to close.

Abstract: Surge control systems are provided for compressors which supply air to a pneumatic load. A signal proportional to the pressure ratio of the outlet pressure to the inlet pressure plus a selected reference pressure is compared to a measured weight flow rate of air through the compressor to provide a vent valve command signal. If the measured pressure ratio plus the reference pressure ratio exceeds the measured flow rate, a surge condition may ensue. The vent valve position command signal causes a venting valve to vent a portion of the air provided to the load, which reduces the measured pressure ratio and increases weight flow rate. During normal operation of the compressor, the vent valve command signal is zero for all values of weight flow rate. A transient control channel is provided which is responsive to the rate of change of the measured pressure ratio and/or measured weight flow rate.

Abstract: Two gas turbine helicopter engines are coupled together for isochronous operation to supply a common load. A control circuit assures that the power delivered to the common load is equally divided between the two engines. The torque of each engine is detected and the torques are compared to established control signals for the engines.

Abstract: In order to limit the acceleration and speed of jet engine accessory equipment when a jet fuel starter is being utilized as a power source to drive the accessory equipment when the main jet engines are disconnected from the jet fuel starter, an acceleration and speed control circuit is provided to control a starter clutch that connects the jet fuel starter to the accessory equipment. The acceleration and speed control circuit compares a signal representing a predetermined maximum acceleration and speed with a signal that represents the rate of rotation of the accessory equipment and generates signals to regulate a control valve which in turn controls the starter clutch.