Kinematics Modeling and Motion Planning of Tendon Driven Continuum Manipulators

Continuum manipulators have important applications in the human–machine interaction fields.The kinematics,dynamics,and control issues of the continuum manipulators are rather different from a conventional rigid-link manipulator.By the aid of Lie groups theory and exponential coordinate representations,the kinematics of the continuum manipulators with piecewise constant curvatures and actuated by tendons is investigated in this paper.On the basis of differential kinematics analysis,the complete Jacobian of the continuum manipulators is derived analytically,and then a new motion planning approach,named as“dynamic coordination method”is presented for the multisegments continuum manipulators,which is a class of superredundant manipulators.The novel motion planning approach is featured by some appealing properties,and the feasibility of the modeling and the motion planning method is demonstrated by some numerical simulations.

Dynamic modeling and beating phenomenon analysis of space robots with continuum manipulators

Space robotics has been used extensively in complex space missions. Rigid-manipulator space robots may suffer from rigid-body collisions with targets. This collision is likely to cause damage to the space robot and the target. To overcome such a problem, a novel ContinuumManipulator Space Robot(CMSR) for performing on-orbit servicing missions is proposed in this paper. Compared with rigid-manipulator space robots, CMSRs are able to perform compliant operations and avoid rigid-body collisions with a target. The CMSR consists of two kinds of flexible components, including solar arrays and continuum manipulators. The elastic vibrations of these flexible components disturb the position and attitude of CMSRs. The beating phenomenon introduced by the energy transfer among these flexible components can cause damage to solar arrays.The complicated dynamic coupling poses enormous challenges in dynamic modeling and vibration analysis. The dynamic model for CMSRs is derived and the mechanism of the beating phenomenon is analyzed in this paper. Simulation results show that an obvious beating phenomenon occurs and the amplitude of the solar arrays increases significantly when the natural frequencies of two kinds of flexible components are close. A method is provided to avoid the beating phenomenon.

Fruit harvesting continuum manipulator inspired by elephant trunk

By combining the investigation of the biomechanics and behavior of elephant trunk in the performance of a wide range of dexterous manipulations,a novel approach in the design and kinematics modeling of a fruit harvesting continuum manipulator was proposed.By comparing the structure of two different species of elephant trunk,a new continuum structure which matched the key features of elephant trunk was designed.Based on analysis of the underlying elephant trunk’s grasping mode,a novel kinematics model was proposed.Contrast to traditional robot kinematics which focused on end effector’s position and posture,the proposed continuum manipulator kinematics focus on the center of manipulator’s position and posture,which is more effective when trunk robot realizing grasp and establishes the foundation for its application.Finally,three typical grasping experiments were implemented.The experiment results showed that the manipulator could conduct wrap/pinch manipulations effectively for both small objects and bigger ones.

Active compliance and force estimation of a continuum surgical manipulator based on the tip-pose feedback

Continuum manipulators have been applied in different surgical scenarios due to their dexterity and multi-DoF(degree of freedom)design compactness.To improve surgery safety,it is preferable to enable active compliance and force sensing abilities for a continuum manipulator.Existing works on active compliance and force sensing often rely on force sensors at the proximal or the distal ends,which inevitably increases the system complexity.In this paper,a shape reconstruction algorithm,a compliant motion controller,and a force estimation method are proposed successively based on the manipulator's tip pose via visual feedback.Four support vector regression(SVR)trainers are constructed and trained to compensate for the actuation residues,which are the differences between the actual actuation lengths outputs at the actuators and the ideal actuation lengths calculated from the estimated shape using the kinematics model,under no-load condition.Then,a compliant motion controller and a force estimation method are realized based on the current actuation residues,compared with the actuation residues under the no-load condition.In this way,no additional sensors are needed as an endoscopic camera is often available in a laparoscopic or endoscopic surgical system.The experiments were conducted on aφ3 mm-continuum manipulator to demonstrate the effectiveness of the proposed algorithms.

Soft Robotics:Morphology and Morphology-inspired Motion Strategy

Robotics has aroused huge attention since the 1950s.Irrespective of the uniqueness that industrial applications exhibit,conventional rigid robots have displayed noticeable limitations,particularly in safe cooperation as well as with environmental adaption.Accordingly,scientists have shifted their focus on soft robotics to apply this type of robots more effectively in unstructured environments.For decades,they have been committed to exploring sub-fields of soft robotics(e.g.,cutting-edge techniques in design and fabrication,accurate modeling,as well as advanced control algorithms).Although scientists have made many different efforts,they share the common goal of enhancing applicability.The presented paper aims to brief the progress of soft robotic research for readers interested in this field,and clarify how an appropriate control algorithm can be produced for soft robots with specific morphologies.This paper,instead of enumerating existing modeling or control methods of a certain soft robot prototype,interprets for the relationship between morphology and morphology-dependent motion strategy,attempts to delve into the common issues in a particular class of soft robots,and elucidates a generic solution to enhance their performance.