An underactuated mechanism is presented as a new finger design for improving grasp adaptability of LARM Hand fingers. Underactuation is discussed as a feasible solution through several design structures for finger adaptability to shape and size of objects to be grasped. The proposed underactuated solution for a new LARM finger is characterized through simulation results in ADAMS environment for operation feasibility and performance.

With rapid development of methods for dynamic systems modeling, those with less computation effort are becoming increasingly attractive for different applications. This paper introduces a new form of Kane's equations expressed in the matrix notation. The proposed form can efficiently lead to equations of motion of multi-body dynamic systems particularly those exposed to large number of nonholonomic constraints. This approach can be used in a recursive manner resulting in governing equations with considerably less computational operations. In addition to classic equations of motion, an efficient matrix form of impulse Kane formulations is derived for systems exposed to impulsive forces.

Singular configurations of parallel manipulators (PMs) are special poses in which the manipulators cannot maintain their inherent infinite rigidity. These configurations are very important because they prevent the manipulator from being controlled properly, or the manipulator could be damaged. A geometric approach is introduced to identify singular conditions of planar parallel manipulators (PPMs) in this paper. The approach is based on screw theory, Grassmann–Cayley Algebra (GCA), and the static Jacobian matrix. The static Jacobian can be obtained more easily than the kinematic ones in PPMs. The Jacobian is expressed and analyzed by the join and meet operations of GCA. The singular configurations can be divided into three classes. This approach is applied to ten types of common PPMs consisting of three identical legs with one actuated joint and two passive joints.

We propose a motor-driven capsule robot based on a sliding clamper (MCRSC), a device to explore the partially collapsed and winding intestinal tract. The MCRSC is powered by wireless power transmission based on near-field inductive coupling. It comprises a novel locomotion unit, a camera, and a three-dimensional receiving coil, all installed at both ends of the locomotion unit. The novel locomotion unit comprises a linear motion mechanism and a sliding clamper. The former adopts a pair of lead-screw and nut to obtain linear motion, whereas the latter anchors the MCRSC to a specific point of the intestinal tract by expanding its arc-shaped legs. The MCRSC is capable of two-way locomotion, which is activated by alternately executing linear motion and anchoring action. Ex vivo experiments have shown that the MCRSC is able to inspect the colon within a time frame of standard colonoscopy.

Lateral-pendulum unicycle robot is a type of single-wheeled mobile robot which utilizes an inverted pendulum mounted laterally for its stabilization and control. Even though this concept was first mentioned in the 1980s, it has not been sufficiently explored especially from the theoretical point of view. Therefore, this robot represents a niche which is still open for more thorough research. This paper presents four contributions to the research of this particular robot. First, the complete model of the robot dynamics is derived and this model can facilitate more accurate study of the robot's static and dynamic behaviors. Secondly, two important constants namely (1) lateral-statics boundary and (2) lateral-statics constant, which are useful for the lateral stabilization, are derived and analyzed. Thirdly, turning constant, required for the control of the turning motion, is derived and used to study the achievable path curvature in maneuvering control. Lastly, dynamics couplings during steady linear motion and steady circular motion are studied and the necessity of integral action in the lateral controller for circular motion is shown and explained. Throughout this paper, numerical simulation is used intensively and two case studies are presented to illustrate the concepts.

In this study, a gait optimization routine is developed to generate walking patterns which demand the lowest friction forces for implementation. The aim of this research is to fully address the question “which walking pattern demands the lowest coefficient of friction amongst all feasible patterns?”. To this end, first, the kinematic structure of the considered 31 DOF (Degrees of Freedom) humanoid robot is investigated and a closed-form dynamics model for its lower-body is developed. Then, the medium through which the walking pattern generation is conducted is presented. In this medium, after designing trajectories for the feet and the pelvis, the joint space variables are obtained, using the inverse kinematics. Finally, by employing a genetic algorithm (GA), an optimization process is conducted to generate walking patterns with the minimum Required Coefficient Of Friction (RCOF). Six parameters are adopted to parameterize the pelvis trajectory and are exploited as the design variables in this optimization procedure. Also, a parametrical study is accomplished to address the effects of some other variables on RCOF. For comparison purposes, a tip-over Stability Margin (SM) is defined, and an optimization procedure is conducted to maximize this margin. Finally, the proposed gait planning procedure is implemented on SURENA III, a humanoid robot designed and fabricated in CAST, to validate the developed simulation procedure. The obtained results reveal merits of the proposed optimal gait planning procedure in terms of RCOF.

Designing and testing flight control algorithms for quadrotor UAVs (unmanned aerial vehicles) is not an easy task due to the risk of possible danger and damage during the practical flight. In order to improve the safety and efficiency of the flight control implementation, a low-cost real-time HILS (hardware-in-the-loop simulation) testbed for quadrotor UAVs is developed in this paper. To realize the HILS testbed, a miniature quadrotor is used as the main body, equipped with a micro AHRS (attitude heading reference system) unit and a self-build DSP (digital signal processor) board. The HILS is implemented by using xPC target. A compact PC/104 computer is utilized as the target computer, and a laptop PC is employed as the host computer. A desktop PC is used as flight visualization computer which runs FlightGear and Google Earth to show visual data, such as orientation and flight path of the quadrotor UAV. This testbed can be utilized for simulating various flight control algorithms, without losing safeness and reliableness. To demonstrate the effectiveness of the proposed testbed, a new nonlinear adaptive sliding mode based stabilization control algorithm is developed and verified on the HILS testbed.

On-line identification of soil parameters is a pre-condition of operating performance optimization and control for unmanned ground vehicles (UGV). Inverse calculation from measured vehicular operating parameters is a prevalent methodology. However, it inherently suffers from a multiple-solution problem caused by the coupling of soil parameters in terramechanics equations and an accuracy problem caused by the influences of state noise and measurement noise. These problems in tractive-force-related soil parameters identification were addressed here for air-cushioned vehicles (ACV) by taking advantage of their additional degree of control freedom in vertical force. To be specific, a g-function algorithm was proposed to solve the multiple-solution problem from reproductive tractive force equations; de-noising techniques consisting of mean-effect strategies, sampling points selection and sample rearrangement were employed to solve the accuracy problem. A series of experiments were conducted to evaluate these techniques at different noise levels and in different soil conditions. They got satisfactory results in terms of data utilization ratio, identification accuracy and performance stability. The contribution of the paper lies in inventing a novel algorithm for unique and accurate identification of tractive-force-related soil parameters without making any simplification to the original terramechanics equation and with robustness to variations of noise level and soil condition.

In this article, a two-dimensional analysis of biped robot sliding dynamics is performed. First, the dynamics of a biped robot based on feet-slip are derived using the coulomb friction model. The state transition can be formulated in the centroid acceleration space whose diagram is defined as a “triangle of sliding friction” (TSF). The TSF's characteristics are explained by focusing on comparison with the cone of friction which has a similar state decision diagram. Next, for the behavioral simulation of a concrete model, a 2-DOF biped robot is used to analyze the sliding features in terms of the asymmetry of the dynamics of each leg. Finally, the sliding characteristics are applied to the two tasks of running and somersaulting. The results show the robot takes short rapid repetitive steps for running based on frictional asymmetry and theoretically based on torque asymmetry can make one revolution using the large angular momentum acquired during sliding motion.

Swing-leg retraction in walking is the slowing or reversal of the forward rotation of the swing leg at the end of the swing phase prior to ground contact. For retraction, a hip torque is often applied to the swing leg at about the same time as stance-leg push-off. Due to mechanical coupling, the push-off force affects leg swing, and hip torque affects the stance-leg extension. This coupling makes the energetic costs of retraction and push-off depend on their relative timing. Here, we find the energy-optimal relative timing of these actions. We first use a simplified walking model with non-regenerative actuators, a work-based energetic-cost, and impulsive actuations. Depending on whether the late-swing hip torque is retracting or extending (pushing the leg forward), we find that the optimum is obtained by applying the impulsive hip torque either following or prior to the impulsive push-off force, respectively. These trends extend to other bipedal models and to aperiodic gaits, and are independent of step lengths and walking speeds. In one simulation, the cost of a walking step is increased by 17.6% if retraction torque comes before push-off. To consider non-impulsive actuation and the cost of force production, we add a force-squared (F2) term to the work cost. We show that this cost promotes simultaneous push-off force and retracting torque, but does not change the result that any extending torque should come prior to push-off. A high-fidelity optimization of the Cornell Ranger robot is consistent with the swing-retraction trends from the models above.

The Derivative-free nonlinear Kalman Filter is used for developing a robust controller which can be applied to underactuated MIMO robotic systems. The control problem for underactuated robots is non-trivial and becomes further complicated if the robot is subjected to model uncertainties and external disturbances. Using differential flatness theory it is shown that the model of a closed-chain 2-DOF robotic manipulator can be transformed to linear canonical form. For the linearized equivalent of the robotic system it is shown that a state feedback controller can be designed. Since certain elements of the state vector of the linearized system cannot be measured directly, it is proposed to estimate them with the use of a novel filtering method, the so-called Derivative-free nonlinear Kalman Filter. Moreover, by redesigning the Kalman Filter as a disturbance observer, it is shown that one can estimate simultaneously external disturbance terms that affect the robotic model or disturbance terms which are associated with parametric uncertainty. The efficiency of the proposed Kalman Filter-based control scheme is tested in the case of a 2-DOF planar robotic manipulator that has the structure of a closed-chain mechanism.

This paper describes an optimized magnetic wheel solution for use in a novel grit-blasting robot intended to be used on the hulls of ships. The grit-blasting robot was designed for conducting surface operations on newly-built ships in dry yards. It can be adapted to curvatures of up to 0.833 m−1; can achieve a total payload of 120 kg and can also be steered. The proposed magnetic wheel solution for robots with such payloads and surface adaptability has not been seen in previous work.

As the magnetic force acting on a magnetic wheel is very sensitive to the working conditions, a mathematical model was built to derive the exact force requirements taking into account the mechanical structure of the robot and its disposition on the ship's hull. In this paper, the design of the wheels was optimized based on the model. Wheels were manufactured according to the optimized results and a prototype robot was constructed. The design was then validated using locomotion tests.