Design of compliant mechanisms using continuum topology optimization: A review

This study presents the design of an underactuated, two-finger, motor-driven compliant gripper for grasping size-varied unknown objects. The gripper module consists of one main frame struc...

Optimal Design of a Soft Robotic Gripper for Grasping Unknown Objects.

Human–machine interfaces (HMIs) are widely studied to understand the human biomechanics and/or physiology and the interaction between humans and machines/robots. The conventional rigid or invasive HMIs that record/send information from/to human bodies have significant disadvantages in practice for long-term, portable, and comfortable usages. To better adapt to natural soft skins, soft HMIs have been designed to deform into arbitrary shapes, and their bendable, stretchable, compressible and twistable properties offer a huge potential in future personalized applications. This paper presents a survey on various soft HMIs in terms of design, sensing, stimulation as well as their applications. Specifically, tactile/motion/bio-potential sensors are categorized for recording various data from human bodies, while stimulators are discussed for information feedback and motion activation to human bodies. It is anticipated that soft HMIs will promote the interaction among humans, machines/robots and environment to achieve desired coexisting-cooperative-cognitive function in a robot system, named as Tri-Co Robot, for the human-centered applications, such as rehabilitation, medical monitoring and human–robot cooperation.

Soft human–machine interfaces: design, sensing and stimulation

This article presents an innovative, motor-driven, three-finger compliant gripper for adaptive grasping of size-varied delicate objects. An optimized compliant finger design is identified numerically through a topology optimization method. A stepper motor is used to actuate three identical compliant fingers, which can operate through elastic bending deformation. Finite-element models are developed to investigate the maximum equivalent stress, input force, and output displacement relations corresponding to the amount of input displacement of the compliant finger. Simulation results show that the proposed finger design is with a lower driving force and a lower maximum equivalent stress during operation comparing to one previous design. The proposed compliant finger is prototyped by three-dimensional printing using thermoplastic elastomer. Experimental results for the input displacement versus input force and input displacement versus geometric advantage relationships of the prototyped finger agree well with simulation results. The developed three-finger soft robotic gripper is mounted on an industrial robot arm to demonstrate its capability in handing size-varied delicate objects, such as egg, fruits, and glass products. Experimental results show that the proposed three-finger gripper can be used to grip object with a maximum weight of 4.2 kg and a maximum object size of 140 mm. The overall weight of the developed three-finger soft robotic gripper is 1.2 kg. The load capacity of the developed gripper can vary according to the friction between gripper and object. The maximum payload of the gripper can be increased to 9.5 kg when an additional antislip foam tape is applied on the grip surfaces of the compliant fingers.

Optimal Design of a Motor-Driven Three-Finger Soft Robotic Gripper

This paper presents the optimal design process of an innovative adaptive compliant gripper (ACG) for fast handling of objects with size and shape variations. An efficient soft-add topology optimization algorithm is developed to synthesize the optimal topology of the ACG. Unlike traditional hard-kill and soft-kill methods, the elements are equivalent to be numerically added into the analysis domain through the proposed soft-add scheme. A size optimization method incorporating Augmented Lagrange Multiplier (ALM) method, Simplex method, and nonlinear finite element analysis with the objective to maximize geometric advantage (which is defined as the ratio of output displacement to input displacement) of the analyzed compliant mechanism is carried out to optimize the design. The dynamic performance and contact behavior of the ACG is analyzed by using explicit dynamic finite element analysis. Three designs are prototyped using silicon rubber material. Experimental tests are performed, and the results agree well with the simulation models. The outcomes of this study provide numerical methods for design and analysis of compliant mechanisms with better computational efficiency, as well as to develop an innovative adaptive compliant gripper for fast grasping of unknown objects.

Guo Feng Huang

Papers

Topology Synthesis and Optimal Design of an Adaptive Compliant Gripper to Maximize Output Displacement

A topology optimization method with constant volume fraction during iterations for design of compliant mechanisms

An Evolutionary Soft-Add Topology Optimization Method for Synthesis of Compliant Mechanisms With Maximum Output Displacement