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FOR USE
Ben Cochran (Project Leader) Kevin Gerhart (Archivist) Eric Hillen (Hardware Manager) Chris Trowbridge (Software Manager) Moving-­‐Head Spotlight Abstract The Stage Stalker is a motion tracking interface which calculates the position of a wireless transmitter and translates this information into a standard control protocol for moving-­‐head, intelligent spotlights in real-­‐time. Moving-­‐head spotlights can move on three axes with high levels of speed and accuracy. A light controlled by the Stage Stalker will be given commands to move in such a way that it appears to follow the transmitter, which can be worn by a person. This technology would provide the live performance and entertainment industry with a new set of creative applications for these pieces of hardware which are already in wide use. KEY Ultrasonic Sensor Ultrasonic Signal Theory of Operation Wireless Transmitter Moving-­‐Head Spotlight DMX512 Position Signal ZigBee Timing Signal Processing and Control Unit (PACU) with ZigBee Receiver Received Ultrasonic Timing Signal Ultrasonic Timing Signal Ultrasonic Receiving Sensors A person will wear the Stage Stalker wireless transmitter, which contains a ZigBee transceiver and an ultrasonic transducer. A time stamp will be generated and transmitted at the same time on both a ZigBee and ultrasonic signal from the transmitter. In the relatively small space of the stage, the ZigBee signal will arrive at the Processing and Control Unit (PACU) almost instantly since it travels at the speed of light (3x108 m/s). The ultrasound waves will travel much slower, at the speed of sound (340 m/s), and arrive at different times to different sensors at known locations around the stage. The time of arrival of the ultrasound signal at the different sensors will then be compared to the time of arrival of the ZigBee signal at the PACU. A time of arrival algorithm will use the time of flight of the ultrasound signal from the transmitter to each sensor to calculate a radius of possible locations for the transmitter. It will calculate the intersection of possible locations from each sensor and use this as the known location of the transmitter. This location will determine the necessary pan and tilt for the moving-­‐head spotlight, whose location is fixed with relation to the known location of each ultrasonic sensor. A control signal using DMX512 lighting protocol will be sent to light to dictate these parameters for the light’s position. The light will move to this position (pointing at the location of the transmitter) and will continue updating, and essentially, follow the person wearing the transmitter. Wireless Transmitter Processing and Control Unit ZigBee Signal Engineering Design Requirements The Stage Stalker… •  must be capable of tracking the transmitter’s position over a confined area defined by a 12.2m x 12.2 m (40’ x 40’) The Stage Stalker will… square. •  perform high-­‐speed motion tracking •  will employ at least 3 sensors for receiving timing in real-­‐time. information from the wireless transmitter. •  act as an interface for a moving-­‐
head spotlight to follow a moving The Wireless Transmitter… object. •  will not exceed a total weight of 5lbs. •  work with one light. •  will withstand vibrations caused by a user’s movements. •  have a wireless transmitter. •  must require no user calibration. •  avoid interference with other •  battery life will meet or exceed 2 hours of operation. wireless devices. •  not require modification to a The Processing and Control Unit… spotlight: it works with existing •  will operate on standard 120VAC. control protocols. •  will refresh the position calculation at least 44 times per second – the refresh rate of the DMX512 lighting protocol. •  unit must output information in the DMX512 protocol via a standard 3-­‐pin XLR connector. Marketing Requirements • 2012-­‐2013 Senior Design Capstone Project • Dr. Nghi Tran, Faculty Advisor • Mr. Gregory A. Lewis, Senior Design Coordinator • Department of Electrical and Computer Engineering • College of Engineering • University of Akron •