A touch-sensing system for precise robotic arm control, using force-sensing resistors (FSR), VHDL and FPGAs

A touch-sensing system, based on force-sensing resistances, FPGAs and VHDL, is presented here, capable of providing precise control of a robotic arm model, thus making it move up or down depending on which of two sensors is pressed.The robotic arm is connected to a step motor able to rotate clockwise or counterclockwise, in order to provide lowering or rising of the arm, respectively.In case that both sensors are stopped being pressed, robotic arm remains to its last obtained position.Both sensors use voltage divider circuit and their analog voltage values act as input to FPGA's ADC converter and both values are presented to seven-segment displays.Three different rotation speed scales are used for both sensors, depending on the exerted pressure and respective LED lights up to present the scale.Additionally, buzzer alarm and half of FPGA's board LEDs are activated if one of the sensors is pressed over a critical value which is dangerous for damaging sensors.Another control implemented in our system, makes the other half of FPGA's board LEDs light up, when a critical time value of continuous step motor operation is exceeded, in order to protect motor from overheating.The system uses DE10-Lite FPGA board with two FSR 402 sensors connected to it.Our system can work with a variety of force sensors and critical input voltage limits can be set by the programmer depending on the application that the system is implemented.