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An ASIC has been developed as a key element of the whole-arm obstacle avoidance (WAOA) system. The WAOA system prevents a teleoperated robotic are from colliding with nearby objects in unfamiliar and sight-limited environments. The WAOA system consists of multiple capacitive proximity sensors attached to all surfaces of a robotic arm and signal processing and communications electronics (1) to communicate impending obstacle contact to the teleoperations control computer that halts movement toward an obstruction and (2) to provide visual feedback to a human operator. The WAOA ASIC performs all analog signal processing associated with control and readout of the capacitive proximity sensor, converts analog sensor signals to digital information, and transmits the digital sensor data to a microcontroller via a shared communications bus. The micro controller preprocesses digital sensor data from as many as 31 sensors and then communicates sensor data to the teleoperations control computer. The WAOA ASIC contains a sensor excitation oscillator, a charge-sensitive input amplifier, a digitally programmable gain amplifier, a synchronous demodulator, an output filter amplifier with digital offset control, a 10-bit ADC, control and status registers, and serial data shift registers. The sensor's digitized proximity measurement value and digital gain setting are loded into an output serial shift register and transmitted to the microcontroller when selected. Conversely control registers are loaded from the serial shift register with control data received from the data concentrator. The WAOA system operates in five modes: setup, acquisition, calibration, diagnostics, and data transmission. The use of an ASIC to control the capacitive sensor allows all signal processing and data communications support electronics to be packaged on a small printed circuit board attached directly behind the sensor. The WAOA sensor system has a response time of approximately 1 msec. It can reliably sense obstructions at a distance of 15 cm, with decreasing sensitivity as the distance increases. |