Real-time Model Inversion Control for Speed Recovery of Hydrostatic Drive Used in the Rotary Head of a Blasthole Drilling Machine

Hydraulic drive systems play an important role in the functioning and performance of Blasthole drilling machines (BHDM) that are utilized extensively in the mining industries for drilling rock formations of different strengths. The rotational velocity of the drill bit is repeatedly changed from the desired value when it moves from one layer to another. It causes a significant loss in the performance and efficiency of the machine. In this article, a model inversion-based control for the BHDM has been developed and implemented on a test setup to recover the speed of the hydraulic drive. The control challenge with BHDM arises due to highly nonlinear dynamics and repeated step loadings. To tackle this, an inverse model-based control technique has been proposed. The observability and controllability of the system are determined graphically using the Bond Graph technique, which is otherwise difficult to evaluate numerically due to the nonlinearity. Dynamic and control performance has been evaluated and compared to the PID control which happens to be a versatile and widely renowned approach. Unlike PID control (where the output parameter of the system is constantly matched with the reference value to determine the input), the input calculation through the proposed control becomes active after a significant change in the stored steady-state values of the speed is noticed. As a result, the proposed control approach achieves its objective without using the initial state of the system and allows the system to function as an open-loop system for most of the time. The controller is activated only when a significant change in the steady-state value of motion is observed and in such a case the system becomes a closed-loop system. Apart from the design of a control algorithm, input shaping is proposed for improving the transient response. The developed model provided satisfactory results resembling a BHDM in real time; hence, the proposed method (with necessary modifications) can be used for other nonlinear systems for similar applications.