This paper analyzes numerically the minimum turning radius of a quad-plane UAV in high-speed flights based on its dynamic model. The smallest turning radius that satisfies the flight conditions for a steady level turn is searched for by numerical optimization at various flight speeds. The turning radius is significantly reduced by utilizing the four rotors mounted on the UAV for rotary-wing mode, although they are not used in the conventional fixed-wing mode of flight. The four rotors allow the UAV to increase its lift and to control its moment in addition to the aerodynamic lift and moment. This enhanced maneuverability of the UAV due to the rotors leads to higher turning performance. The numerical results also show that the reduction in turning radius depends on the flight speed.

This paper reveals that the turning radius of a tiltrotor UAV during high-speed flights can be significantly reduced by utilizing the redundancy in control inputs. Based on a dynamic model of the UAV, the flight conditions of steady level turns are analyzed to numerically search for the minimum turning radius when all the actuators installed in the UAV are utilized. Numerical results indicate that adding lift with sub-rotors installed for rotary-wing mode makes it possible to increase the roll angle during level turns while reducing the turning radius. The tilt angle of main rotor can also be chosen within a certain range to reduce the turning radius. The feasibility of such steep turns is checked by numerical simulations using a feedback control.

This paper demonstrates that singular configuration of a two-link robot arm is advantageous in doing the task of pulling or lifting up a heavy object with small joint torques. As a result of numerical optimization, the initial configuration that minimizes the joint torques necessary for the task is close to the singular configuration where the arm is stretched out. The singular configuration has the dynamic feature that the joint angle vector can be accelerated in a certain direction almost independently of the mass of the object. Then, the joint torques can generate large kinetic energy efficiently at the singular configuration, and the energy can be utilized to pull or lift up the object. The experimental results show that the dynamic feature is practically useful, even when a feedback control is applied in order to make the object follow a planned trajectory.

This paper evaluates the dynamic and kinematic properties of a prismatic mechanism and shows its capabilities in performing home manipulation tasks when integrated into a robotic arm. Our design is motivated from the observation that human hand motions often follow a linear trajectory when manipulating everyday objects. We present the mechanical design for a light-weight, energy-efficient robot named PRISM that emphasizes translational motion. By simulating the dynamics equations and comparing the structure of commonly used anthropomorphic arms and our proposed arm, we verify that translational motion is more energy efficient with PRISM, and the robot can maneuver itself in narrower places. Through simulation experiments using state of the art manipulation planning algorithms, we analyze the success rates of PRISM and an anthropomorphic robot arm in performing basic tasks. The simulation experiments center on pick-and-place tasks in cluttered kitchen scenes. We show a real-world prototype of PRISM and perform several manipulation experiments with it.

We propose a singularity-based mechanism (SBM) to exploit the singular configuration that improves the angular acceleration instead of constraining the movement. The tradeoff between the responsiveness and the range of motion is achieved by varying a length of linkage in the SBM. In this paper, we clarify the responsiveness of the SBM using the dynamics analysis. For the demonstration, we build an experimental SBM system with the high responsiveness, a practical range of motion, and a size comparable to a human arm. In the experiment, the effectiveness of the SBM is shown in a vertical lifting task. The characteristic of the SBM that generates a large acceleration at start is similar to the human arm moved by a muscle. The similarity between the SBM and the human arm is analyzed in terms of the static torque.

This paper discusses the advantages of singular configurations of a two-link robot arm in achieving tasks of pulling or lifting a heavy object. Optimal base location and arm motion for minimizing the joint torques are examined by numerical simulations, and the base location where the robot arm is near a singular configuration at the start time of task is optimal. It is shown analytically that joint torques can supply energy to the system composed of the robot arm and the object efficiently near singular configurations of the arm. The energy supply rates at two singular configurations are derived based on the equations of motion of the system.

This paper presents a study on the optimal base location and arm motion of a mobile manipulator for door opening task. Numerical simulation results show that the base location where the manipulability of the two-link arm is almost degenerated at the start and end points of door opening is optimal.We show by analysis that the location has an advantage in supplying kinetic energy to the door by using torques at the joints of arm. In order to represent properly the arm motion near a singular point of manipulability, the rotational motion of the door is parameterized by piecewise fifth order polynomials of time, and the parameters of polynomials are optimized to minimize the joint torques.

This paper deals with the feedback stabilization problem for a two-wheeled mobile robot which moves in the presence of obstacles. A state feedback controller is proposed based on Lyapunov control. First, we choose a potential function (Lyapunov function) whose value is minimum at a desired point and maximum on the surfaces of obstacles. And then, we construct a control input by multiplying the gradient vector of the potential function by a matrix composed of a negative definite symmetric one and a skew-symmetric one. It is shown that the system with the controller converges to one of critical points of the potential function. When the potential function has some critical points other than the minimum at the desired point, in order to avoid convergence to those points, the controller is modified. As a result, the controlled system converges to the desired point avoiding collision with obstacles.