Design and development of voice/joystick operated microcontroller based intelligent motorised wheelchair

The foldable composite mechanical assembly of the chair is driven by two 24 V/120 Watt DC motors having an engagement/disengagement clutch and speed reduction gear mechanism with built-in electromagnetic locking under the command of a 80C196KC based microcomputer. The speed and direction of the chair which can be controlled by pre-decided suitable voice commands or manually, using a joystick switch are directly proportional to the linear displacement of the joystick in forward or reverse directions. The speaker adaptable language independent isolated word recognition system (IWRS) for a definite vocabulary of words to best suit the user´s requirements has been developed and successfully demonstrated. The microcomputer with 64 k bytes of user selectable memory receives the coded digital signals from the IWRS on being properly recognized voice commands in order to control the function of the chair accordingly. The technique of signal processing for extraction of acoustic parameters, removal of redundant information, intensity and time normalization, and pattern matching etc. have well been simulated on PC for their best performance and later implemented on a hard wired microcontroller based system for achieving real time/near real time operations. Special emphasis has been attributed to the design of a motor driver switching module in order to achieve effective and energy saving driving using high current power MOSFETs. These devices are arranged in H-bridged configurations to reverse the motor supply voltage for bidirectional control. The idea of proximity sensing, a new concept has been introduced for the first time to provide more situational awareness to the vehicle on processing the signals reflected from the surrounding objects for collision avoidance