Passive ultrasonic RFID elevator positioning reference system

An apparatus for measuring a position of a moveable platform, comprising:

• a plurality of transponder modules comprising:
• an RF transmitter adapted to emit an RF signal;
• and
• an ultrasonic receiver adapted to receive an ultrasonic signal
• wherein at least two of said plurality of transponders are disposed about said position to be measured;
• at least one transceiver module affixed to said moveable platform comprising:
• an ultrasonic transmitter adapted to emit an ultrasonic signal;
• an RF receiver adapted to receive an RF signal;
• a timing mechanism for measuring a plurality of durations between an emission of said ultrasonic signal and a receipt of said RF signal;
• and
• a computing mechanism for processing said plurality of durations to compute said position.

A method for determining position, comprising the steps of:

• depositing a plurality of transponder modules for receiving an ultrasonic signal and emitting an RF signal at fixed positions;
• depositing at least one transceiver module for emitting at least one ultrasonic signal and receiving said plurality of RF signals at a desired position;
• emitting said ultrasonic signal;
• receiving at least two of said plurality of RF signals;
• measuring a plurality of durations of time between said emission of said ultrasound signal and said receipt of said plurality of RF signals;
• and
• determining a position of said transceiver module from said durations of time.

A method for measuring a position of a moveable platform, comprising the steps of:

• affixing at least one transceiver module to said moveable platform said transceiver module comprising:
• an ultrasonic transmitter adapted to emit an ultrasonic signal;
• an RF receiver adapted to receive an RF signal;
• a timing mechanism for measuring a plurality of durations between an emission of said ultrasonic signal and a receipt of said RF signal;
• and
• a computing mechanism for processing said plurality of durations;
• disposing a plurality of transponder modules each at a fixed position said transponder modules comprising:
• an RF transmitter adapted to emit an RF signal;
• and
• an ultrasonic receiver adapted to receive an ultrasonic signal;
• emitting from said at least one transceiver module said ultrasonic signal for receipt by said plurality of transponder modules and starting a timing mechanism;
• receiving said ultrasonic signal with said plurality of transponder modules each emitting an RF signal encoded with a unique code;
• receiving said plurality of emitted RF signals with said RF receiver;
• using said timing mechanism to measure at least one duration of time between emitting said ultrasonic signal and receiving each of said plurality of emitted RF signals;
• and
• computing said position of said moveable platform using said fixed positions and said at least one measured duration of time.