In this article, we introduce a new soft finger with a pneumatic-actuated movable joint that is optimized and characterized in terms of the degrees of freedom (DoF), workspace, and fingertip force. The finger consists of one soft link as the body and the bending pneumatic joint as the actuator. Due to the additional translation and rotation movement capabilities of the joint, carried out by two stepper motors, the finger can bend in any direction while having different lengths, thanks to a configurable bending point. This results in more dexterity for the finger when dealing with a target inside its 3D workspace by increasing the number of configurations it can use to reach the target and exert force. The finite element method (FEM) and the Nondominated Sorting Genetic Algorithm II (NSGA-II) algorithm are applied to optimize the joint geometry and so maximize the bending angle and minimize the joint dimensions. Furthermore, the variations of each design parameter and consequent effects on the optimization objectives are analyzed. The optimal geometrical parameters are used to fabricate a prototype with silicone rubber. Tests on the bending angle and tip force variability are conducted on the prototype to validate the numerical modeling. The experimental results show that the finger exerts force up to 650 mN with a response time of fewer than 3 s. The stiffness of the finger can be changed by applying pneumatic pressure in the hollow space inside the link. This consequently varies the amount of applied force at the tipping point of the finger up to two times.

中文翻译：

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灵巧的机械手指的设计和优化：结合了滑动，旋转和软弯曲机制，同时最大限度地提高了灵活性并减小了尺寸

在本文中，我们介绍了一种带有气动可动关节的新型软手指，该关节在自由度（DoF），工作空间和指尖力方面得到了优化和表征。手指由一个软链接作为主体，由弯曲的气动接头作为致动器。由于关节的附加平移和旋转运动能力（由两个步进电机执行），得益于可配置的弯曲点，手指可以在任何方向上弯曲，同时具有不同的长度。通过增加手指可用于到达目标并施加力的配置数量，在处理其3D工作空间内的目标时，手指可获得更大的灵活性。应用有限元方法（FEM）和非支配排序遗传算法II（NSGA-II）算法来优化关节几何形状，从而最大程度地提高弯曲角度并最小化关节尺寸。此外，分析了每个设计参数的变化以及对优化目标的影响。最佳几何参数用于制造硅橡胶原型。在原型上进行了弯曲角度和尖端力可变性的测试，以验证数值模型。实验结果表明，手指施加的力高达650 mN，响应时间少于3 s。手指的刚度可以通过在连杆内部的中空空间内施加气压来改变。