Abstract: An inverter is connected between a source of DC power and a three-phase AC induction motor, and a micro-processor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .THETA., where .THETA. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands of electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor.

Abstract: An inverter (34) which provides power to an A.C. machine (28) is controlled by a circuit (36) employing PWM control strategy whereby A.C. power is supplied to the machine at a preselectable frequency and preselectable voltage. This is accomplished by the technique of waveform notching in which the shapes of the notches are varied to determine the average energy content of the overall waveform. Through this arrangement, the operational efficiency of the A.C. machine is optimized. The control circuit includes a micro-computer and memory element which receive various parametric inputs and calculate optimized machine control data signals therefrom. The control data is asynchronously loaded into the inverter through an intermediate buffer (38). In its preferred embodiment, the present invention is incorporated within an electric vehicle (10) employing a 144 VDC battery pack (32) and a three-phase induction motor (18).

Abstract: A crane operating aid comprises a load moment computer and a number of transducers which monitor crane parameters such as boom length, boom angle, and boom reaction forces. The computer then calculates the percentage of load capacity as a function of the crane manufacturer's published load rating tables. In cranes having booms which are luffed by a plurality of hydraulic lift rams, boom reaction forces are determined by providing separate pressure transducers on the lower or high pressure end of each ram. The upper or low pressure ends of the rams are in fluid communication with one another, requiring only a single pressure transducer. Each transducer generates an output signal as a function of the pressure which it is monitoring. The signals from the transducers associated with the high pressure ends of the rams are averaged and the difference between the output signal of the transducer associated with the low pressure ends of the rams and the average signal is used to generate a reaction force signal.

Abstract: A crane operating aid comprises a load moment computer and a number of sensors which monitor crane parameters, such as boom length, boom angle, slewing angle, and boom reaction forces. The computer then calculates the percentage of load capacity as a function of the crane manufacturer's published load rating tables. Absolute encoding digital optical sensors are employed to monitor linear or angular displacement between portions of the crane which are operatively moveable with respect to one another. The digital output signals from the various sensors are then fed to the computer for use in its calculations. Each sensor comprises a detector made up of a light emitting element which is spaced from a light receiving element and an encoder disc which is mounted for displacement with respect to the detector and operates to present a series of tracks intermediate the light emitting portion and light receiving portion of the detector. Each track comprises a series of alternatingly opaque and transparent portions.

Abstract: A crane operating aid comprises a load moment computer and a number of transducers which monitor crane parameters such as boom length, boom angle, and boom reaction forces. The computer then calculates the percentage of load capacity as a function of the crane manufacturer's published load rating tables. The computer is disposed near the crane operator to facilitate interaction between the two and actively solicits crane condition information from him through a prompting scheme which initially poses a series of status requests to the operator. The operator must supply appropriate responses to the status requests prior to operating the crane. The computer also can display any of the input parameters monitored by the transducers. A plurality of alarms of ordered urgency are provided which indicate various overlimit conditions. Both minimum and maximum operator controlled set points are provided.