Modelling and control of a five‐degrees‐of‐freedom pneumatically actuated magnetic resonance‐compatible robot

Abstract

The results demonstrated that the robotic system with the designed controller was effective in both position control and trajectory tracking.

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“…< 0 and system (7) is bounded with the control law (20). As a result, V 3 and z 1 , z 2 , z 3 converge to arbitrarily small values depending on the tuning parameters c 1 , c 2 , c 3 .…”

“…As a result, accurate models of the pressure dynamics typically rely on continuous pressure measurements in the cylinder chambers [42]. Consequently, the pressure dynamics was generally disregarded in the design of previous controllers for similar pneumatic systems [20], [21], [24]. In this work, the pressure dynamics due to valve, pipe, and cylinder chamber was experimentally evaluated with a step command issued to the proportional valve and a simultaneous pressure measurement.…”

“…Recently, the successful use of piezoelectric actuators was demonstrated in [14], [15] with a novel motor driver, achieving a reduction in SNR below 15%. New piezoelectric actuators have recently been proposed [16], offering some potential for the future, although at present they are still limited to small-range [17]- [20], since it produces minimum alterations to the MRI environment and, compared to hydraulics, it is clean and inexpensive. However, pneumatic valves should be placed far from the scanner, since they employ electric currents that can interact with the magnetic field.…”

“…In some notable solutions this issue was addressed placing the valves inside a special shielded enclosure in the scanner room [17], [18]. In other works it was considered advantageous placing the valves outside the scanner room [12], [20], [21]. While the first approach reduces the length of the pipes, the second requires a simpler design and limits the use of electric components in the scanner room.…”

“…Recently, a new stepper motor design was proposed in [22], which offers smaller size and simpler construction at the cost of reduced power and limited positioning accuracy. The most common control approaches for direct-drive pneumatic actuations with long supply lines employed in the MRI environment are PID schemes [17], [18], [20] and Sliding Mode Control (SMC) schemes, such as [23]- [25] and references therein. Recently, higher accuracy was achieved with a Time Delay Controller (TDC) in [26], which however did not account for the pressure dynamics due to valves and pipes.…”