PWM Control of SMA Actuated Blowout Preventer Using PLC

Conventionally, hydraulic actuators are used in blowout preventers (BOP) to regain well pressure control in oil/gas drilling or production. As drilling moves to deeper and deeper undersea, the hydraulic actuators are not able to meet the API mandates in response time. An innovation of BOP's actuators was proposed to use the shape memory alloy (SMA) recently. This paper presents design and implementation of the Pulse Width Modulation (PWM) regulated Proportional-Derivative (PD) control using a Programmable Logic Controller (PLC) for the SMA actuators used in BOP. The SMA actuator holds a few outstanding features compared to its conventional counterparts, and thus has been used in a variety of applications. On the other hand, SMA is nonlinear, and a sophisticated controller is required to ensure its stability and robustness. In the paper, after a short review of the prototype of the SMA actuated BOP, the design and implementation of the PWM PD controller is presented, followed by the testing results of position control of SMA actuated BOP.