Haiying Wen

Kinematic Model and Analysis of an Actuation Redundant Parallel Robot With Higher Kinematic Pairs for Jaw Movement

A jaw movement robot that can simulate jaw movement and reaction forces in temporomandibular joints (TMJs) of a man will find many applications in dentistry, food science, and biomechanics. The TMJ is the most sophisticated joint in the human body, and its compound movements are not given sufficient consideration when a jaw robot is designed. Based on the biological finding about the mastication system and its motion characteristics, this paper proposes an actuation redundant parallel mechanism for the jaw movement robot and designs the actuation systems and models the TMJ in a higher pair kinematic joint. The prototype of the proposed jaw movement robot is presented, consisting of six prismatic-universal-spherical linkages for muscle groups of mastication and two point contacts for left and right TMJs. This robot has four degrees of freedom but is driven by six actuators. Each prismatic-universal-spherical linkage is made up of a rotary motor, a prismatic joint, a universal joint, and a spherical joint. The closed-form solution to the kinematics is found. This novel robot is evaluated by simulations of kinematics, workspace, and a chewing movement experiment.

Coaxial twin-shaft magnetic fluid seals applied in vacuum wafer-handling robot

Compared with traditional mechanical seals, magnetic fluid seals have unique characters of high airtightness, minimal friction torque requirements, pollution-free and long life-span, widely used in vacuum robots. With the rapid development of Integrate Circuit (IC), there is a stringent requirement for sealing wafer-handling robots when working in a vacuum environment. The parameters of magnetic fluid seals structure is very important in the vacuum robot design. This paper gives a magnetic fluid seal device for the robot. Firstly, the seal differential pressure formulas of magnetic fluid seal are deduced according to the theory of ferrohydrodynamics, which indicate that the magnetic field gradient in the sealing gap determines the seal capacity of magnetic fluid seal. Secondly, the magnetic analysis model of twin-shaft magnetic fluid seals structure is established. By analyzing the magnetic field distribution of dual magnetic fluid seal, the optimal value ranges of important parameters, including parameters of the permanent magnetic ring, the magnetic pole tooth, the outer shaft, the outer shaft sleeve and the axial relative position of two permanent magnetic rings, which affect the seal differential pressure, are obtained. A wafer-handling robot equipped with coaxial twin-shaft magnetic fluid rotary seals and bellows seal is devised and an optimized twin-shaft magnetic fluid seals experimental platform is built. Test result shows that when the speed of the two rotational shafts ranges from 0–500 r/min, the maximum burst pressure is about 0.24 MPa. Magnetic fluid rotary seals can provide satisfactory performance in the application of wafer-handling robot. The proposed coaxial twin-shaft magnetic fluid rotary seal provides the instruction to design high-speed vacuum robot.

A biomimetic chewing robot of redundantly actuated parallel mechanism

Purpose - This paper aims to describe how a novel biomimetic chewing robot was designed, including its motion, force, control and mechanical designs, and shows some initial experiments about motion tracking.

Application of triune parallel‐serial robot system for full‐mission tank training

Purpose – The purpose of this paper is to build a seven‐degrees of freedom (DOF) parallel‐serial robot system which has the advantage of mechanical novelty and simplicity compared with the existing platforms, and to share the experience of converting a popular motion base to an industrial robot for use in full‐mission tank training processes of three armored arms.Design/methodology/approach – By studying the concept of the robot system, a novel parallel‐serial robot with seven DOF driven by electrical servo motors is built. And the transmission modules and Hooke joints are explored and designed in detail. Then the inverse kinematics based on coupling compensation and time‐jerk synthetic optimization methods for trajectory planning of the simulator are presented and further discussed in order to satisfy the requirements of high stability and perfect performance. In advance, the feasibility and applicability of this triune parallel‐serial robot system are verified.Findings – A prototyped test shows that the...

Mandibular movement experiment of a masticatory robot

A masticatory robot that can simulate jaw movement and occlusal forces like human will find many applications in dentistry, food science and biomechanics. Based on the biological finding about mastication system and its motion characteristics, an actuation redundant parallel mechanism with point contact higher kinematic pair (6PUS-2HKP) for simulating mastication movement is introduced. The coordinate system of the robot is established. The kinematics of this redundantly actuated spatial parallel mechanism is derived. In order to test the robots performance, a mouth opening and closing trajectory was planned. Experiment result shows that the robot can perform one full mouth opening and closing cycle within 1 s and the robot is able to reproduce the mouth opening and closing movements like humans.

Experimental verification of workspace and mouth-opening movement of a redundantly actuated humanoid chewing robot

Purpose – This paper aims to verify the workspace and movement performance of a redundantly actuated humanoid chewing robot. Design/methodology/approach – A redundantly actuated humanoid chewing robot with 6-PUS linkages and two higher kinematic pairs (HKPs) is introduced. The design of HKPs is specified by mimicking the temporomandibular joint (TMJ) structure obtained through a computed tomography scan of the mastication system. The border movement, mouth-opening trajectory and velocity of subjects’ lower incisor point are measured by using the mandibular kinesiograph. Based on the kinematics, the envelope of the workspace is analyzed. The workspace and mouth-opening movement experiments are carried out. The border movement of the lower incisor point is measured. The mouth-opening trajectory is planned and tested on the chewing robot. Findings – Comparing with measurement results of border movement and mouth-opening movement of human, it is shown that the humanoid chewing robot can meet the workspace req...

Design and Kinematics Performance Analysis of a Novel Jaw Movement Robot

To achieve the high bio-imitability requirements,a novel jaw movement robot is proposed based on mechanical biomimetic principles.Firstly,according to the biomechanical properties of mandibular muscles,such as unsymmetrical distribution,forces in different directions and the non-coplanar joints connecting maxillary and mandible,a robot that simulates the jaw movement is built based on the 6-PUS(prismatic-universal-spherical) parallel mechanism.Then,its inverse kinematics solution equation and Jacobian matrix are derived,and the analysis of kinematics performance such as workspace,singularity and flexibility is carried out to verify the feasibility of the mechanism design.Finally,a jaw movement experiment is conducted on the platform of virtual prototype to analyze the trajectory and the drive system of the robot.And the movement trajectory of the robot obtained is compared with the real movement of the human mandibular.The results indicate that the presented jaw movement robot meets the authenticity requirements of the human mandibular movement trajectory.

Contact kinematics of spatial higher kinematic pairs of a masticatory robot

The temporomandibular joint (TMJ) is a complex bilateral articulation, and its movements are a combination of hinge movement and gliding movement guided by its articular surfaces. A masticatory robot with higher kinematic pairs (HKPs) simulating TMJ behavior is introduced. Kinematic equations of the HKPs are derived based on three-dimensional kinematics of rigid bodies and differential geometry. Position, velocity and acceleration of the contact points are analyzed according to the characteristics that the condyle movement involves rotation and translation simultaneously. Given a target trajectory, the position of contact point, velocity and acceleration relative to articular surface of fossa are obtained by simulation based on the contact kinematics of the HKPs. The result provides a useful tool for studying kinematics behavior of human TMJs.

Trajectory measurement of human mandible and movement test of a chewing robot

In order to control a chewing robot in biologically faithful fashion with humans, the trajectory of the lower incisor point of mandible is measured by using mandibular kinesiograph. The main parameters of the envelope of lower incisor point movement are found. Based on the measurements and the characteristics of the basic functional mandibular movements, the trajectory of the robot is planned. An actuation redundant parallel mechanism with point contact higher kinematic pair for simulating mastication movement is introduced. The actual border movement experiment is carried out to verify the performance of the chewing robot. It is shown that the chewing robot can meet the movement space requirements.

Simulation of a 6-PUS jaw robot and a new mechanism inspired by masticatory system

A jaw robot based on the 6-PUS parallel mechanism was introduced according to the biomechanical properties of mandibular muscles. For a given mandibular trajectory to be tracked, the inverse kinematics solution is derived and Jacobian matrix formulated from differential kinematics is found. Kinematics performances, such as constant orientation workspace and manipulability are simulated via numerical method. These indices show that the parallel mechanism has enough flexible workspace without singularity, and has a good motion transmission performance for human chewing movement. In order to reproduce jaw motions and mechanics that match the human jaw function truthfully with the conception of bionics, the temporomandibular joints (TMJs) are taken into account. Another novel actuation redundant mechanism for the jaw robot is proposed based on mechanical biomimetic principles, which has four degrees of freedom, but is driven by six actuators.