Magnetically actuated capsule robots promise minimally invasive diagnosis and therapy in the gastrointestinal (GI) tract, but existing systems largely neglect control of capsule pitch, a degree of freedom critical for contact-rich interaction with inclined gastric walls. This paper presents a nonlinear, model-based framework for magnetic pitch control of an ingestible capsule robot actuated by a four-coil electromagnetic array. Angle-dependent magnetic forces and torques acting on embedded permanent magnets are characterized using three-dimensional finite-element simulations and embedded as lookup tables in a control-oriented rigid-body pitching model with rolling contact and actuator dynamics. A constrained model predictive controller (MPC) is designed to regulate pitch while respecting hardware-imposed current and slew-rate limits. Experiments on a compliant stomach-inspired surface demonstrate robust pitch reorientation from both horizontal and upright configurations, achieving about three to five times faster settling and reduced oscillatory motion than on-off control. Furthermore, an extended Kalman filter (EKF) fusing inertial sensing with intermittent visual measurements enables stable closed-loop control when the camera update rate is reduced from 30 Hz to 1 Hz, emulating clinically realistic imaging constraints. These results establish finite-element-informed MPC with sensor fusion as a scalable strategy for pitch regulation, controlled docking, and future multi-degree-of-freedom capsule locomotion.

翻译：磁驱动胶囊机器人有望在胃肠道实现微创诊断与治疗，但现有系统大多忽略了对胶囊俯仰角的控制——这一自由度对于与倾斜胃壁进行密集接触式交互至关重要。本文提出了一种基于非线性模型的磁控俯仰角控制框架，用于由四线圈电磁阵列驱动的可摄入胶囊机器人。通过三维有限元仿真表征作用于嵌入式永磁体的角度依赖型磁力与力矩，并将其作为查找表嵌入考虑滚动接触与执行器动力学的面向控制的刚体俯仰模型中。设计了约束模型预测控制器（MPC），在遵循硬件施加的电流与转换速率限制的同时调节俯仰角。在柔性仿胃表面进行的实验表明，系统能从水平和直立两种构型实现稳健的俯仰角重定向，其稳定时间较开关控制缩短约3至5倍，且振荡运动显著减弱。此外，通过扩展卡尔曼滤波器（EKF）融合惯性传感与间歇视觉测量，在摄像头更新率从30 Hz降至1 Hz（模拟临床实际成像限制）时仍能实现稳定的闭环控制。这些结果确立了有限元分析指导的MPC结合传感器融合技术作为一种可扩展策略，适用于俯仰角调节、受控对接及未来多自由度胶囊运动控制。