Tin Lun Lam

Omnidirectional Steering Interface and Control for a Four-Wheel Independent Steering Vehicle

This paper presents an omnidirectional steer-by-wire system for a four-wheel independent steering vehicle. The system consists of an extended steering interface and a behavior-based steering controller. The extended steering interface provides a novel manipulation way to vehicle driver. The driver can control the vehicle in traditional way or omnidirectionally without any mode switching operation. The reservation of the traditional driving way makes the driver adapt the novel steering interface easily. The steering interface also has a force-feedback function to synchronize the extended steering interface and the orientations of wheels so as to improve vehicle handling. The behavior-based steering controller is designed for controlling the orientations of wheels. It acts as virtual linkage among each wheel to minimize wheel slip resulted by the misalignment of wheels. As there is no trajectory planning needed in the control algorithm, the proposed controller is especially suitable for a nonautonomous vehicle, the driving path of which cannot be predetermined.

A flexible tree climbing robot: Treebot - design and implementation

This paper proposed a novel tree climbing robot “Treebot” that has high maneuverability on an irregular tree environment and surpasses the state of the art tree climbing robots. Treebots body is a novel continuum maneuver structure that has high degrees of freedom and superior extension ability. Treebot also equips with a pair of omni-directional tree grippers that enable Treebot to adhere on a wide variety of trees with a wide range of gripping curvature. By combining these two novel designs, Treebot is able to reach many places on trees including branches. Treebot can maneuver on a complex tree environment, but only five actuators are used in the mechanism. As a result, Treebot can keep in compact size and lightweight. Although Treebot weighs only 600 grams, it has payload capability of 1.75 kg which is nearly three times of its own weight. On top of that, the special design of the gripper permits zero energy consumption in static gripping. Numerous experiments have been conducted on real trees. Experimental results reveal that Treebot has excellent climbing performance on a wide variety of trees.

System and design of an Omni-directional vehicle

This paper presents a novel vehicle named omni-directional Kart (OK-1), in which robotic technologies, such as 4 wheel independent driving (4WID) and 4 wheel independent steering (4WIS), are integrated to decouple the motions of translation and rotation from each other. As a result, omni-directional motions such as zero radius turning (ZRT) and lateral parking (LP) are realized for better vehicle steerability and mobility in limited space.

Biologically inspired tree-climbing robot with continuum maneuvering mechanism

Treebot is the first tree-climbing robot that is capable of climbing from a tree trunk to a branch. The robot employs several design principles adapted from arboreal animals, including claw gripping and inchworm locomotion, with a certain artificial optimization to achieve high maneuverability on irregular-shaped trees. Treebot is composed of a pair of tree grippers that permits Treebot to attach to a wide variety of trees with a wide range of gripping curvature, and a novel continuum maneuvering structure that provides high maneuverability and adaptability. In the robot actuation, only five actuators are necessary. Although Treebot weighs only 600 gr, it has a payload capability of 1.75 kg, which is nearly three times its own weight. This paper describes the design process and specifically addresses the robot locomotion and optimization of gripping force. Experimental results demonstrate the robots ability to climb trees with high maneuverability.

Climbing Strategy for a Flexible Tree Climbing Robot—Treebot

In this paper, we propose an autonomous tree climbing strategy for a novel tree climbing robot that is named Treebot. The proposed algorithm aims to guide Treebot in climbing along an optimal path by the use of minimal sensing resources. Inspired by inchworms, the algorithm reconstructs the shape of a tree simply by the use of tactile sensors. It reveals how the realization of an environment can be achieved with limited tactile information. An efficient nonholonomic motion planning strategy is also proposed to make Treebot climb on an optimal path. This is accomplished by the prediction of the future shape of the tree. The study that is presented in this paper also includes the formulation of Treebot kinematics and an analysis of the workspace of Treebot on different shapes of a tree. Numerous experiments have been conducted to evaluate the proposed autonomous climbing algorithm and to unveil the ability of Treebot.

Omni-directional steer-by-wire interface for four wheel independent steering vehicle

In this paper, an omni-directional steer-by-wire interface for four wheel independent steering vehicle is presented. The proposed steering interface is an extension of a traditional steering interface that provides three steering inputs. By combination of which, driver can control the vehicle in traditional way or omni-directionally without any mode switching operation. The reservation of the conventional steering behavior makes driver easy to adapt the novel steering interface. The force feedback controller is designed to synchronize the extended steering interface and the orientations of wheels so as to improve vehicle handling. Hardware-in-the-loop simulations are conducted to verify the hardware prototype and examine the proposed algorithms.

Mechanical design and implementation of a soft inflatable robot arm for safe human-robot interaction

In this paper, a novel soft inflatable arm is proposed for telepresence robots. It is capable of imitating human arms to realize remote interaction. The new proposed arm using a very common and low cost inflatable material, and it is very light, which weight is only about 50 grams, but can well realize agile movement by driving three tiny cables installed in shoulder joint and elbow joint, respectively. Meanwhile, the proposed cable driven mechanism also allows connecting numbers of joints easily. The soft inflatable can work just by pumping air with very low pressure (7.32 ± 3.45 kPa), and allows human directly and safely contact without any external sensors. Moreover, to solve the challenge problems of soft joint deformation, the kinematic modeling of the joint with deformation compensation is also developed. Experimental results show that the soft inflatable arm can agilely move for remote interaction. The workspace and velocity are also close to an adults arm movement space and normal motion speed.

Motion planning for tree climbing with inchworm-like robots

This paper proposes a global path- and motion-planning algorithm that enables inchworm-like robots to navigate their way up tree branches. The intuitive climbing space representation method proposed here greatly simplifies the path-planning problem. The dynamic programming algorithm can be used to identify the optimal path leading to the target position in the target direction according to the constraints and requirements specified. The planned path can be applied in any tree-climbing robot that utilizes the nonenclosure gripping method. An efficient motion-planning algorithm for continuum inchworm-like robots is then developed to enable them to climb along the planned path with a high degree of accuracy. In comparison with the method proposed in our previous study, the method proposed herein significantly improves consistency between the planned path and the motions of the robot, and therefore makes it more practical to implement the motion-planning algorithm in trees of different shapes. The paper also describes hardware experiments in which the proposed planning algorithm is applied to enable inchworm-like robots to climb real trees, thus validating the proposed planning algorithm in practice.

Traction force distribution on omni-directional four wheel independent drive electric vehicle

This paper proposes an optimal traction force distribution for omni-directional four wheel independent steering (4WIS) and four wheel independent drive (4WID) vehicle. The proposed force distribution algorithm is aimed to enhance the vehicle stability with minimum cost. The algorithm avoids the use of any feedback information of vehicle motion such as linear velocity as this information is difficult to measure accurately and the price of the measuring equipment is very high. As a result, the implementation cost can be reduced and at the same time avoid improper force distribution due to the inaccurate measured information. Moreover, the proposed algorithm does not involve any parameter tuning. It makes the algorithm easy to implement. The proposed algorithm can also be applied to any steering types of 4WID vehicle such as typical two wheel steering (2WS) as 4WIS is the general case of any steering configuration. Simulation results reveal that the performance of the proposed force distribution is superior to the uniform force distribution which is commonly used in 4WID vehicle.

Novel Design of Gaits on Space Station for Dynamic Disturbance Minimization

In this paper, we propose a novel design of gaits for space manipulators so as to minimize the dynamic disturbance on a space station. Without modifying their joint configuration, we first propose the use of our previous developed gripping methodology. It combines the concepts of wheels motion in parallel grippers to reduce the swing motions in conventional gaits. For the proposed gaits, three major aspects are considered including 1) linear motion; 2) turning; and 3) exterior transition. Based on the conventional modeling approach for fixed base space manipulators, we extend the method to formulate the dynamic coupling during wheels motion. It is to visualize the manipulator as a prismatic joint with its gripping base moving with wheels motion. Also, we develop an experimental platform for verification. For disturbance analysis, various simulations have been conducted. Results have validated that the proposed gaits generate the lowest disturbance on a space station.