Wagner Tanaka Botelho

Motion Analysis with Experimental Verification of the Hybrid Robot PEOPLER-II for Reversible Switch between Walk and Roll on Demand

We propose a newly renovated mobile robot PEOPLER-II (Perpendicularly Oriented Planetary Legged Robot), and addresses its motion analysis for switching its locomotion from leg-type to wheel-type and vice versa. For the leg-type locomotion, particularly in a transitional state of sitting or standing, we propose a control method based on minimization of the total energy cost using the distribution of the motor power payload in the hip and knee joints, in addition to the method of keeping the same payload factor. Also, we discuss robot configurations for switching between the two locomotion types by considering environmental factors such as walking gaits, ground inclination angle and robot’s traveling direction. Knee joint position of a pivotal foot determines knee ahead and knee behind gaits. In each switch, we check such characteristics as the hip joint rotation direction, robot center trajectory, and necessary total power in a practical point of use. Then we build three beneficial switching cycles aiming for moderate use of a motor, rider’s comfort, and power saving. Finally, we demonstrate the switching by considering the aim and verify that the results of the analysis become useful for enabling switching on demand.

Smooth switching phases of a mobile robot from leg-type to wheel-type and vice versa

This paper presents smooth switching phases utilized in the mode change between leg-type and wheel-type locomotion for ascending and descending a slope. The phases are classified into three, i.e, walking, mode change, and rolling phases. In each case, we simulate the robot motion to visualize for verification. Also, we show that the balanced control between right and left side of the robot in the leg-type and wheel-type is generated in the experiment.

Trajectory estimation of a skid-steering mobile robot propelled by independently driven wheels

This paper analyses a mobile robot with independently rotating wheels travelling on uneven but smooth ground, including ascending or descending surfaces. We formulate a mathematical expression for the energy cost of the robots movement. For our analysis, we utilise the principle of virtual work and assume that the robot moves with a fixed arrangement of wheel axes and without using a steering handle. The mathematical model reveals that the coefficient of friction and the payload distribution dominate the wheel behaviour, including slipping and skidding. We minimise the virtual work expression to determine the robots motion complying with driven wheels. The model also enables us to estimate trajectories for different ground conditions. A hybrid robot, PEOPLER-II, is used to demonstrate the predicted motions, including turns and spins, by following angular velocity control rules. Experimental data verifies that the proposed formulation and minimisation of virtual work are valid techniques for predicting a robots trajectory. The method described is widely applicable to wheeled robots having independently driven wheels.

Software and Hardware control of a hybrid robot for switching between leg-type and wheel-type modes

One of the objectives of the paper is to describe the hybrid robot PEOPLER-II (Perpendicularly Oriented Planetary Legged Robot) with regard to switching between leg-type and wheel-type. Our robot has an easier design and control system than other hybrid robots. The software and hardware control in the process of performing five robot tasks are considered. These are the walking, rolling, switching, turning and spinning. In the switching task, we show the control method based on minimization of total energycost. Also, the hardware components and their interconnections are described. The graphical user interfaces utilized in the simulation and experiment are demonstrated. The walking, rolling and the switching without reverse rotation and arm motion are verified in simulation and with real robot, in addition to turning and spinning.

Estimation and verification of the trajectory forms generated by a legged sliding robot

This paper presents an 3D algorithm to estimate the motion trajectory of a four legged sliding robot considering the ground friction coefficient and the payload distribution at leg ends during walk on a flat ground including ascending or descending slopes. We formulate mathematical expression for estimating energy cost of motion utilizing the principle of virtual work under the condition where the robot moves by alternating pivotal feet having hemispherical form at their ends. Then we minimize the sum of the virtual work for determining actual robot motion. Results of the minimization make it possible to simulate the motion behaviors for visualizing robot trajectory in different traveling environments. Additionally, we verify simulation results by demonstrating the walk with functions of turn and spin as a legged type of the hybrid robot PEOPLER-II. Hence the proposed algorithm is useful for clarifying the robot motion behaviors.