Hisashi Date

Adaptive locomotion of a snake like robot based on curvature derivatives

This paper presents locomotion control for a robotic snake that adaptively travels over rugged terrain using obstacles as supports. This kind of locomotion can typically be found in snakes in nature. The snake robot dealt with in this paper has an articulated structure in which all joints are actively driven. For locomotion on a flat terrain, joint torques distributed according to the curvature derivative of the body curve has been proved to be optimal under the condition that there is no lateral slippage at every part of the body. In this paper, the same method is applied to locomotion using two kinds of environmental supports; a narrow corridor surrounded by smoothly curved walls and a peg.

Locomotion control of a snake-like robot based on dynamic manipulability

We discuss autonomous locomotion control of a snake-like articulated robot with passive wheels. Such a robot has a quite different mechanism in locomotion from that of other locomotion systems, namely, it has no driving wheel and moves only by bending its body. Hence the locomotability depends on its posture. In order to evaluate the locomotability, we utilize a notion of dynamic manipulability which has been applied to a robot manipulator. We also propose a simple controller based on this manipulability. Simulation results show that a certain periodic winding motion is automatically generated.

Simultaneous control of position and orientation for ball-plate manipulation problem based on time-State control form

This paper deals with the ball-plate manipulation problem considered as a typical but complicated model of a driftless nonholonomic system. Due to a strong nonlinearity of the ball-plate system, a state equation of the kinematic model cannot be transformed into a chained form, which is known to be effective in constructing a feedback control law for some driftless nonholonomic systems. To address this problem, we utilize a time-state control form, a kind of canonical form which covers a broader class of systems than the chained form. This form is first applied to two separate subproblems, position control, in which the planar position of the ball is controlled but not the orientation, and orientation control, in which the orientation is controlled without changing the positional relation between the ball and the plates. It turns out that there exists a linearly uncontrollable subspace in the transformed subsystem, which turns into controllable by a change of coordinates. This implies that the system has the structure of a system with two generators. We propose a control strategy using iterative changes of coordinates, ensuring convergence in the neighborhood of the origin. Finally, we unify the subproblems into simultaneous control of position and orientation, i.e., the whole configuration of the system. The important idea in the simultaneous control is the coordinate transformation, which enables us to avoid a singular point. Results of simulations show that the proposed method achieve robustness to a measurement noise and perturbation of radius of the ball.

Locomotion control of a snake robot with constraint force attenuation

We deal with the locomotion control of a snakelike articulated robot with passive wheels. The robot gains propulsion by means of constraint forces on the wheels caused by actuating the joints. The so-called serpentine movement is known to be an effective gait on a flat ground. Our goal is to achieve such motion by autonomous gait generation, i.e., without giving any winding gait beforehand. Therefore we utilize a notion of manipulability to evaluate the locomotability and propose a control method capable of reducing the constraint forces. The results of simulations show that smooth motion is generated.

Control of 3D Snake-Like Locomotive Mechanism Based on Continuum Modeling

An effective control method that achieves movement over a small ridge as an example of three-dimensional (3D) snake-like creeping locomotion is presented. The creeping robot is modeled as a continuum with zero thickness capable of generating bending moment at arbitrary points. Under a simplified contact condition, the optimal bending moment distribution in terms of a quadratic cost function of input can be obtained as a function of curvature by solving an isoperimetric problem. The solution is well suited to an articulated body consisting of finite number of links. The model is demonstrated through simulations and experiments using a prototype robot to be effective for traversing smooth 3D terrain.Copyright

Development of a wheeled mobile robot "octal wheel" realized climbing up and down stairs

This paper proposes an eight-wheeled robot which is able to climb over the uneven terrain for rescue, de-mining other works. In order to perform these works without human assistance, robots must have the ability to move on rugged terrain. Wheeled vehicles have advantages for moving efficiency and speed but the disadvantage is that the diameter of the wheel limits which obstacles can be surmounted. This paper proposes a mechanism which eliminates the disadvantages of a wheeled system. This mechanism is applied to a self-standing type eight-wheeled robot which is able to climb up and down stairs by utilizing a command form remote controller. Experimental results demonstrate the effectiveness of this mechanism and robot.

Control of a snake robot in consideration of constraint force

This paper deals with an autonomous locomotion of a snakelike articulated robot with passive wheels. Using the non-slip condition of the wheels, the robot gains propulsion by means of constraint forces on the wheels caused by bending the joints. Our goal is to achieve the so-called serpentine movement known to be an effective gait on a flat ground with automatic gait generation, i.e., without giving any winding gait beforehand. We utilize a notion of manipulability to evaluate the locomotability and propose a controller capable of reducing the constraint forces. The results of simulations show that smooth winding motion is achieved.

An electricity-free snake-like propulsion mechanism driven and controlled by fluids

Unlike ordinary snake-like robots, a propulsion mechanism that does not rely on electricity for control and actuation is proposed in this paper. Analysis of a snakes propulsion based on a continuum model unveils that the lateral undulation can be achieved by bending the body at torque proportional to the curvature derivative of the body curve, as observed in muscular activities of biological snakes. Thanks to the simplicity of this principle, a pure mechanical structure comprising a fluid servomechanism can be realized. The proposed propulsion mechanism also consists of gears that propagate the joint angle information to the posterior joint to mechanically simulate curvature derivative.

Manipulation problem of a ball between two parallel plates based on time-state control form

This paper deals with the ball-plate problem being considered as an effective model for nonholonomic constraints, and gives simultaneous control method for both the position and orientation of the ball based on the time-state control form.

Real world experiments of an autonomous mobile robot in the pedestrian environment

This paper reports experiences of the Tsukuba Challenge 2009 and 2010, or the Real World Robot Challenge. The challenge aims at promoting practical technologies for autonomous mobile robot working in pedestrian environment. The robot has to travel 1 km along a specified route without human aid, modifying the environments, or causing any dangers to human safety. This paper discusses failure due to unexpected behavior of pedestrians in the 2009 challenge and solutions for success in the challenge 2010.