Masaki Yamakita

Swing-up Control of Inverted Pendulum Using Pseudo-State Feedback:

Swing-up control, that is the transfer of a pendulum from a pendant state to the inverted one, is a good laboratory experiment of optimal control theory for non-linear control systems. The optimal control can be determined by the maximum principle and obtained as a function of time. Since the control is, however, determined in a feedforward fashion, the control is not robust to disturbances and uncertainties of the system, and the transfer of the state of the pendulum is not assured. In the paper, a robust swing-up control using a subspace projected from the whole state space is proposed. Based on the projected state space or pseudo-state, the control input is determined depending on the partitioning of the state as a bang-bang type control. The control algorithm is applied for a new type of pendulum (TI Tech pendulum), and the effectiveness and robustness of the proposed control are examined by experiments.

Tele-virtual Reality Of Dynamic Mechanical Model

In this paper we propose a technique for tele-virtual reality of dynamic mechanical models, which means that one dynamic mechanical model can be shared by peoples in distant places. Since a stabil- ity issue due to time delays arises in the system, we employed a scattering technique developed for a tele- operator system and a kind of passive adaptive con- trollers. Furthermore, restrictions due to a simple digi- tal implementation of the scattering transformation are discussed and some conditions for stability are shown. The proposed method is applied to a remote tug of war system and the effectiveness is verified.

Swing up control of inverted pendulum

A bang-bang-type state feedback control algorithm which can swing up a pendulum from a pendant position to an upright position is proposed. In the control system a conventional LQ control method is also employed around the upright position to maintain the pendulum in the upright position after the pendulum has been swung up to this position by the bang-bang control. The control system was constructed and the validity of the control method was examined experimentally. Since the pendulum is attached by a hinge to a rotating arm fixed to a direct drive motorshaft, it contains fewer uncertainties introduced by transmission mechanisms, e.g., a belt and gears in a linear-type inverted pendulum. The advantages of the designed pendulum are that it is small and saves experimental space, and that the robustness of control algorithms can be easily tested with it since known parasitics can be added as uncertainties in the control loops, e.g., a flexible arm can be used instead of a rigid arm.<<ETX>>

Biped gait generation and control based on a unified property of passive dynamic walking

Principal mechanisms of passive dynamic walking are studied from the mechanical energy point of view, and novel gait generation and control methods based on passive dynamic walking are proposed. First, a unified property of passive dynamic walking is derived, which shows that the walking systems mechanical energy increases proportionally with respect to the position of the systems center of mass. This yields an interesting indeterminate equation that determines the relation between the systems control torques and its center of mass. By solving this indeterminate equation for the control torque, active dynamic walking on a level can then be realized. In addition, the applications to the robust energy referenced control are discussed. The effectiveness and control performances of the proposed methods have been investigated through numerical simulations.

Robust swing up control of double pendulum

Inverted pendulums are typical examples of unstable system and have been used for the verification of designed control systems and/or control education in laboratories. In particular, the control of a double inverted pendulum has been known as a good example to show the power of the modern control theory. In this paper we consider about robust state transfer control method of a double pendulum, i.e., swing up control of the pendulum from the hanging position to the upright position. First, we propose a control method based on a energy principle. Secondly, a more robust control method in which the state transfer is realized through a limit cycle is presented. The effectiveness of the proposed methods is shown by the experiments.

A snake-like swimming robot using IPMC actuator/sensor

We constructed a snake-like swimming robot using IPMC actuator, and verified swimming motion based on numerical simulation and experiments. In applying periodic inputs with appropriate frequency and phase shift, the snake-like robot is capable of smooth propulsion. It is known that IPMC has a sensor function that IPMC films generate electromotive voltage when bending or being deformed. By using the sensor function into the snake-like robot, it is considered that autonomous propulsive motion can be realized by feedback of the sensor signal. In this paper, we consider the autonomous locomotion of the snakelike swimming robot with IPMC actuator/sensor, and verify the realization of swimming motion by feedback of the sensor signal. Furthermore, the efficiency of the autonomous locomotion is investigated

A New Inverted Pendulum Apparatus for Education

Abstract An inverted pendulum fixed by a hinge to a rotating arm is proposed for control researches and for control laboratory experiments. It does not have the driving means such as belt or wire which yields uncertainties, and can also be used for the experiments of a running inverted pendulum. A controller is designed for a double inverted pendulum taking the uncertainties into consideration. A partial nonlinear controller is studied to expend the conventional linear one for linearizing the part of the nonlinear pendulum model.

Development of an artificial muscle linear actuator using ionic polymer–metal composites

We are developing an artificial muscle linear actuator using ionic polymer-metal composites (IPMC)—electro-active polymers that bend in response to electric stimuli—and the goal of our study is applying the actuator to robotic applications, especially to a biped walking robot. In this paper, we will describe the structure of the actuator and an empirical model of the actuator which has two inputs and one output, and whose parameters are identified from input-output data. Based on the empirical model, basic experiments and position control of the linear actuator are demonstrated. Then, we consider walking control of a small-sized biped walking robot. In the application we assume that the developed actuators are connected both in series and in parallel to a joint of the walking robot so that the actuators supply enough torque to the robot, and that they are stretched and compressed enough. It is shown throughout simulations that the biped walking robot with the actuators can walk on level ground with a period synchronized with the period of the input signal.

A novel gait generation for biped walking robots based on mechanical energy constraint

This paper proposes novel energy-based gait generation and control methods for biped robots based on an analysis of passive dynamic walking. First, we discuss the essence of dynamic walking using a passive walker on a gentle slope from the mechanical energy point of view. Second, we propose a simple and effective gait-generation method, which imitates the energy behavior in every walking cycle considering the zero-moment point condition and other factors of the active walker. The control strategy is formed by taking into account the features of mechanical energy dissipation and restoration. Following the proposed method, the robot can exhibit a natural and reasonable walk on a level ground without any gait planning and design in advance. The effectiveness of the method is examined through numerical simulations and experiments.This paper proposes a novel energy-based control law for biped robots based on an analysis of passive dynamic walking. Firstly we discuss the essence of dynamic walking using a passive walker on a gentle slope. In the second, we propose a simple and effective control law which imitates the energy behavior in every cycle considering the ZMP condition and other factors of the active walker. The control strategy is formed by the feature of mechanical energy dissipation and restoration. By the effect of the proposed method, the robot can exhibit natural and reasonable walk on a level ground without any gait design in advance. The validity of the proposed method is examined by numerical simulations and experiments.

Control of locomotion and head configuration of 3D snake robot (SMA)

In this paper, we propose a winding control technique using a physical index of horizontal constraint force for a 3D snake-like robot, and it is shown that a winding motion of the robot can be realized with small joint torque. If it approaches a target point, it is necessary to raise the head and to work like a manipulator. Therefore, a control method of the head configuration using a criterion function, which can be used in both redundant and insufficient number of link cases is proposed. In order to show the validity of the proposed methods, we constructed a snake like robot called SMA. Using the experimental system, we show that the winding pattern with which the robot can avoid singular postures is generated automatically, and head position and head orientation can be controlled properly.