A Variable Curvature Continuum Kinematics for Kinematic Control of the Bionic Handling Assistant

Abstract

We present a new variable curvature continuum kinematics for multisection continuum robots with arbitrarily shaped backbone curves assembled from sections with three degrees of freedom (DoFs) (spatial bending and extension, no torsion). For these robots, the forward kinematics and the differential forward kinematics are derived. The proposed model approach is capable of reproducing both the constant and variable backbone curvature in a closed form. It describes the deformation of a single section with a finite number of serially connected circular arcs. This yields a section model with piecewise constant and, thus, a variable section curvature. Model accuracy and its suitability for kinematic real-time control applications are demonstrated with simulations and experimental data. To solve the redundant inverse kinematics problem, a local resolution of redundancy at the velocity level through the use of the robot's Jacobian matrix is presented. The Jacobian is derived analytically, including a concept for regularization in singular configurations. Experimental data are recorded with Festo's Bionic Handling Assistant. This continuum robot is chosen for experimental validation, as it consists of a variable backbone curvature because of its conically tapering shape.

A disposable continuum endoscope using piston-driven parallel bellow actuator

“…Previous works [8], [9] formulated the kinematic model using internal pressure and the length of each bellow as joint space variables, both of which rely on direct pressure control. Inspired by these works, this paper proposes a closed-form kinematic model for parallel bellow actuators.…”

“…The tip position vector x and the rotation matrix R representing the tip orientation can be expressed as in (6)(7)(8), resulting in the configuration to task space mapping F T as:…”

“…Existing works [8], [9] applied direct control on pressurization (i.e. set a pressure reference using fluid pumps).…”

“…The proposed device in this work was inspired by the Bionic Handling Assistant by Festo [8] and catheter based continuum robots [9], and it takes the form of pneumatically actuated endoscope with a parallel bellow actuators (PBA) [9][10][11][12] forming a steerable tip. We propose that pressure lines and therefore bellow extensions in this work are controlled using independent electromechanically driven syringes.…”

Soft Robotics：Structure, Actuation, Sensing and Control

“…。将光导纤维嵌入机器人本体，利用内部光强 的变化检测机器人的触觉 [76] 或者变形 [77][78] 。将导电 材料缠绕在弹性内核上制成可延展导电线，嵌入到 气动三维软体臂测量各腔道的长度和弯曲变化 [79] 。 智能材料在外界物理场的作用下可以变形，而利用 其变形时产生的电压等信号也可以作为传感器来使 用。如利用 SMA 制作的人工肌肉具有自感知能 力 [80] ，利用介电弹性体变形时电容的变化来检测压 力 [81] ，将 IPMC 作为传感器用于水下航行器 [82] [85] ；用系统 辨识的方法可建立输入气压和构型空间参数的关 系 [86] 。 但是 PCC 模型只适用于固定曲率的运动学求 解，对于变曲率的软体机器人运动学问题，需要尝 试新的方法，如将软体连续臂分为多段，每段近似 曲率恒定 [87][88] 。对于流体驱动弹性体和纤维增强制 动器等超弹性材料软体机器人，因其本构关系比较 复杂，学者们多采用有限元分析来研究几何参数对 运动学的影响 [89][90] 。从变形前后的几何关系来分析 其变形机理 [7] SFAKIOTAKIS M，KAZAKIDI A，TSAKIRIS D P.…”