PWM controller design of a hexapod robot using FPGA

Motor control mechanism on a robotic platform has been dominated by microcontroller-based system for the past decade. With the advancement of the reconfigurable hardware platforms such as field programmable gate array (FPGA), such control mechanism is being ported to the platform in order to improve efficiency and achieves higher performance. This paper presents the FPGA implementation of the servomotor control technique which is applied for a six-legged robot platform. The hexapod robot consisted of 18 continuous servomotors with 3 servos on each leg. Each of the servomotors is assigned with single pulse width modulation (PWM) output and could be individually controlled by the main controller. To enable smooth movement of the hexapod, all the PWM output are synchronized based on a simple tripod gait movement. The servo motor controller is implemented in the Spartan-3 FPGA chip and the hardware design is described in Verilog Hardware Description Language (HDL). The controller design is simulated and verified using Xilinx's ISE Simulator (ISim). Initial hardware implementation also has been conducted on several basic movements on the hexapod such as standing-up, forward and backward movement. Overall, the implementation of the servomotor controller in an FPGA has offered several advantages in terms of circuit design flexibility and simultaneous command executions when compared to conventional microcontroller-based system.