Wenzeng Zhang

Super under‐actuated multi‐fingered mechanical hand with modular self‐adaptive gear‐rack mechanism

Purpose – The purpose of this paper is to present recent work designing a mechanical robotic hand for self‐adaptive grasping, human‐like appearance, which can be used in a humanoid robot. Conventional robotic devices are relatively complex, large, cumbersome and difficult to be installed in a humanoid robot arm. Under‐actuated robot hands use less motors to drive more rotating joints, thus to simplify the mechanical structure, decrease the volume and weight and finally lower the difficulty of control and the cost.Design/methodology/approach – A novel under‐actuated finger mechanism is designed, which is based on a gear‐rack mechanism, spring constraint and an active sleeve middle phalanx. The principle analyses of its self‐adaptive grasp and end power grasping are given. A new multi‐fingered hand named as TH‐3R Hand is designed based on the finger.Findings – The design finger mechanism can be used in a robotic hand to make the hand obtain more degrees of freedom (DOF) with fewer actuators, and good graspi...

Under-actuated passive adaptive grasp humanoid robot hand with control of grasping force

Conventional dexterous hands have too many DOFs, their driver systems are too big to be installed in a humanoid robot arm, and their controls are tool complex. This paper develops an under-actuated passive adaptive grasp humanoid robot hand named TH-1 hand with control of grasping force. With humanoid appearance and size, TH-1 hand is light, fewer DOFs, and can be easily controlled. Its motors and driver circuit boards are embedded in itself. These features make it fit to be installed in a humanoid robot arm. In addition, for stably grasping operation, a mechanical finger with control of grasping force is designed and applied in TH-1 hands index. To get more DOFs with fewer drivers, a novel under-actuated passive adaptive grasp mechanical finger is design and applied in TH-1 hands thumb.

Passive adaptive grasp multi-fingered humanoid robot hand with high under-actuated function

This paper proposed a design idea of a novel under-actuated finger mechanism, and designed the finger mechanism. The finger has no actuator in itself, is only driven by the other finger joints and object grasped. The finger is similar to a human finger and can be easily arranged in series to realize a finger with super under-actuation and high integration. It can be mounted in humanoid robot hand to make the hand obtain more DOFs with less actuators, and good grasping function of shape adaptation, decrease the requirement of control system. This paper analyzed the relationship between the grasping force of the finger and its design parameters, proposed the design principle of structure optimization of the finger. Based on the finger, a multi-fingered humanoid robot hand: TH-2 Hand has been designed. TH-2 Hand has many excellent features: high personification, super under-actuation and be very compact, easy to real-time control, small volume, light in weight, strong grasping function, etc.

DEVELOPMENT OF MULTI-FINGERED ROBOTIC HAND WITH COUPLED AND DIRECTLY SELF-ADAPTIVE GRASP

This paper presents a coupled and directly self-adaptive underactuated (CDSA) grasp mode, which has hybrid functions: coupled grasp and directly self-adaptive grasp. A novel multi-pulley-belt finger mechanism with springs is designed based on CDSA grasp mode. Compared with traditional coupled underactuated fingers or directly self-adaptive underactuated fingers, the grasp process of the new finger is more humanoid and its stability is better. Force analysis and size optimization rules of the finger are given. A multi-fingered robotic hand, CDSA hand, based on the CDSA finger is developed, whose control system adopts a digital signal processor (DSP) circuit module with a keyboard as its communication interface. The CDSA hand has five fingers, six DC motors, and 15 joint DOF, nine of which are CDSA joint DOF. The appearance and actions of CDSA hand imitate human hand, whose size is 1.5 times of human hand. CDSA hand weighs 1.6 kg and can grasp objects up to 0.5 kg. Simulation and experimental results show that CDSA hand is able to realize CDSA grasp mode effectively.

GCUA Humanoid Robotic Hand with Tendon Mechanisms and Its Upper Limb

Upper limbs of human beings are extremely special and significant, which obtain crucial function to achieve manipulations intelligently and dexterously. Gesture-Changeable Under-Actuated (GCUA) grasping function is presented to improve the capability of robotic hands to achieve humanoid manipulations with low dependence on control and sensor feedback systems, which includes traditional under-actuated (UA) grasping motion and special pre-bending (PB) motion. Based on GCUA function, GCUA Hand II is developed, which has 5 fingers and 14 DOF. All the fingers use similar tendon mechanisms and motors to achieve GCUA function. With GCUA Hand II, a humanoid robot upper limb system is designed, which has two 3-DOF arms actuated by stepper motors and two 14-DOF hands actuated by DC motors. The control system includes four parts: a computer, a FPGA motion controller, a driver module, and a user module, which can control the upper limb system to do various movements dexterously and exactly. With C++ language, a spatial motion program is designed to assist researchers to determine spatial motions of the upper limb system. This system has a great prospect in the field of rehabilitation engineering, extremely environmental manipulation, humanoid robotics and social services.

A DEXTEROUS AND SELF-ADAPTIVE HUMANOID ROBOT HAND: GCUA HAND

Gesture-changeable under-actuated (GCUA) function is put forward to make traditional under-actuated hands feel easy to grasp different objects and do simple operations dexterously, simultaneously, this function can lower control difficulties of robotic hands. Based on GCUA function, a GCUA hand based on pulley-belt mechanism is designed in detail and manufactured. The Hand can grasp different objects self-adaptively and change its initial gesture dexterously before touching objects. The hand has 5 fingers and 15 DOFs, each finger utilizes screw-nut transmission, flexible drawstring constraint and belt-pulley under-actuated mechanism to realize GCUA function. The analyses on grasping static forces and grasping stabilities are given. The analyses and experimental results show that GCUA function is very nice and valid. The hands with GCUA function can meet the requirements of grasping and operating with lower control and cost, which is the middle road between traditional under-actuated hands and dexterous hands.

A Robot for Welding Repair of Hydraulic Turbine Blade

This paper proposed a scheme of using rail-free multifunctional robot in onsite repair of hydraulic turbine blade for large-scale axial-flow and Francis runners. The robot processes such functions as profile detection and measurement, air-gouging cleaning, grinding, welding and so on. The robots main body is composed of an all-position rail-free mobile platform and a multiple degree-of-freedom (DOF) manipulator. The mobile platform, on which the manipulator equipped with all kinds of exchangeable operating tools is mounted, adheres to the surface of the hydraulic turbine blade to be repaired. The operator can control the robot to carry out repairing work automatically through man-machine conversation interface of a monitoring system. Simulation of the process of welding repair using the robot was conducted. And prototypes of key components of the robot system were developed. Preliminary experimental results proved the feasibility of scheme of the repairing robot.

A Dexterous and Self-adaptive Humanoid Robot Hand: Gesture-Changeable Under-Actuated Hand

A novel concept called gesture-changeable under-actuated (GCUA) function is proposed to improve the dexterities of traditional under-actuated hands and reduce the control difficulties of dexterous hands. Based on the GCUA function, a new humanoid robot hand, GCUA Hand is designed and manufactured. The GCUA Hand can grasp different objects self-adaptively and change its initial gesture dexterously before contacting objects. The hand has 5 fingers and 15 DOFs, each finger is based on screw-nut transmission, flexible drawstring constraint and belt-pulley under-actuated mechanism to realize GCUA function. The analyses on grasping static forces and grasping stabilities are put forward. The analyses and Experimental results show that the GCUA function is very nice and valid. The hands with the GCUA function can meet the requirements of grasping and operating with lower control and cost, which is the middle road between traditional under-actuated hands and dexterous hands.

TWO-DOF COUPLED AND SELF-ADAPTIVE (COSA) FINGER: A NOVEL UNDER-ACTUATED MECHANISM

A large amount of effort has been devoted to design better under-actuated robot hands. The most widely adopted approaches include rigid coupled hands and self-adaptive hands. The objective of this research is to design a robot finger which combines advantages of both ways and overcomes their disadvantages. The concept of coupling and self-adaptation (COSA) was introduced. A linkage-based two-DOF (degree of freedom) COSA robot finger was designed, optimized and studied in this paper. The theoretical analysis and the experiments on the finger show that it is able to execute human-like motion and adaptive grasps in multiple patterns. The research exposes a promising novel under-actuated mechanism for hands design with wide applications.

LISA Hand: Indirect self-adaptive robotic hand for robust grasping and simplicity

Humanoid robotic hand is one of most impressive research focus in robotics. There are two important requirements in robotic hands: on the one hand, a hand has a good humanoid appearance and sizes and can grasp almost all of common objects, on the other hand, the same hand is very simple in structure, very easy in control and very low in cost. Most of present dexterous robotic hands could not balance above two aspects. In searching for simple architecture and effective grasp at once, a novel under-actuated robotic hand is designed and manufactured and could achieve the above requirements perfectly, which is called Linkage Indirectly Self-Adaptive Under-actuated Hand, LISA Hand. The key of the LISA Hand is special and simple structure of its fingers. The indirectly under-actuated LISA finger can utilize the inverse forces from objects grasped to realize action of the next joint without any motor. Each of LISA fingers is composed of multiple-class block-linkage-slot transmission mechanisms, multiple springs and only one motor with a reducer. The LISA Hand has 5 fingers, 14 joint DOFs and only 5 motors. All fingers in the LISA Hand are similar. The thumb has two joints, and each of the other four fingers has three joints. Self-adaptation for good grasping performance is designed as the main function of the LISA finger. The grasping principle, process and force analysis of LISA Hands are given. Force analysis shows that the LISA Hand is valid and could be regarded as an end-effecter of humanoid robots.