Taddese Addisu Z, Slawinski Piotr R, Obstein Keith L, Valdastri Pietro
Mechanical Engineering Department, Vanderbilt University, Nashville, TN, USA.
Mechanical Engineering Department, Vanderbilt University, Nashville, TN, USA; Division of Gastroenterology, Hepatology, and Nutrition, Vanderbilt University Medical Center, Nashville, TN, USA.
Rep U S. 2016 Oct;2016:1139-1144. doi: 10.1109/IROS.2016.7759192. Epub 2016 Dec 1.
In this paper, we demonstrate velocity-level closed-loop control of a tethered magnetic capsule endoscope that is actuated via serial manipulator with a permanent magnet at its end-effector. Closed-loop control (2 degrees-of-freedom in position, and 2 in orientation) is made possible with the use of a real-time magnetic localization algorithm that utilizes the actuating magnetic field and thus does not require additional hardware. Velocity control is implemented to create smooth motion that is clinically necessary for colorectal cancer diagnostics. Our control algorithm generates a spline that passes through a set of input points that roughly defines the shape of the desired trajectory. The velocity controller acts in the tangential direction to the path, while a secondary position controller enforces a nonholonomic constraint on capsule motion. A soft nonholonomic constraint is naturally imposed by the lumen while we enforce a strict constraint for both more accurate estimation of tether disturbance and hypothesized intuitiveness for a clinician's teleoperation. An integrating disturbance force estimation control term is introduced to predict the disturbance of the tether. This paper presents the theoretical formulations and experimental validation of our methodology. Results show the system's ability to achieve a repeatable velocity step response with low steady-state error as well as ability of the tethered capsule to maneuver around a bend.
在本文中，我们展示了一种通过串联机械手在其末端执行器处使用永磁体驱动的系留磁胶囊内窥镜的速度级闭环控制。利用实时磁定位算法实现了闭环控制（位置上的2个自由度和方向上的2个自由度），该算法利用了驱动磁场，因此不需要额外的硬件。实施速度控制以创建平滑运动，这对于结直肠癌诊断在临床上是必要的。我们的控制算法生成一条样条曲线，该曲线通过一组大致定义所需轨迹形状的输入点。速度控制器沿路径的切线方向起作用，而辅助位置控制器对胶囊运动施加非完整约束。管腔自然地施加了一个软非完整约束，同时我们对系绳干扰的更精确估计和临床医生远程操作的假设直观性都施加了严格约束。引入了一个积分干扰力估计控制项来预测系绳的干扰。本文介绍了我们方法的理论公式和实验验证。结果表明，该系统能够实现具有低稳态误差的可重复速度阶跃响应，以及系留胶囊在弯道处操纵的能力。
