Pendulum Mode Research Articles

Experimental study of biped dynamic walking

An experimental study of a biped robot is presented. A new scheme named the "linear inverted pendulum mode" is utilized for controlling a biped walking on rugged terrain. The authors developed a six-DOF biped robot, "Meltran II," which has lightweight legs and moves in a two-dimensional vertical plane. To investigate the effects not well discussed in the theory, the authors carried out two experiments, the support phase experiment and the support exchange experiment. The support phase experiment was carried out to check the actual dynamics of a biped walking under the proposed control. It was shown that the dynamics of the robot can be regarded as linear even though the mass of the legs, which was neglected in the theory, exists. The support exchange experiment was performed to check leg support exchange. The authors found that a smooth leg support exchange is achieved by making the foot contact with a certain vertical speed and holding two-leg support for a certain short period. Based on these results, a whole biped control system was implemented. In the authors' experiment the robot walked over a box of 3.5 cm height at a speed of 20 cm/s.

Study of Dynamic Walk Control of a Biped Robot on Rugged Terrain - Derivation and Application of the Linear Inverted Pendulum Mode -

This paper introduces a control method for biped walking on rugged terrain. We assume a biped robot which has a mass body and massless legs, and which is restricted to move in a vertical plane. We apply constrain control to the body of the robot so that it moves on a particular straight line and rotates at a constant angular velocity. As the result of such control, the dynamics of the center of mass of the body becomes completely linear. We also notice that the dynamics of the body does not depend on the slope of the line on which the center of mass of the body is constrained. We call such motion of the ideal model ""Linear Inverted pendulum Mode"". The limitation of the condition under which this method works is also discussed. After these consideration, we have developed the control scheme of the biped walking on rugged terrain. Under the control based on the linear inverted pendulum mode, walking on a particular rugged terrain is shown to be equivalent to walking on a level surface. Finally, it is shown that by using ankle torque, our method becomes robust and can be applied to a real biped robot with mass legs. This is ascertained by simulation.

Some practical considerations in the design of in-vessel transporters

Some design constraints common to various types of in-vessel transporter are identified and discussed with reference to ITER. These constraints are determined by considering the effects of the transporter structural characteristics on the overall in-vessel remote handling system and the effects of the in-vessel environments on materials and components of the transporter. For structural design the importance of transporter natural frequency in addition to static deflection is identified. The tendency of transporters to exhibit a low-frequency torsional pendulum mode when handling heavy loads at large vertical distances from the equator of the vacuum vessel is demonstrated and its significance for remote handling is discussed. The effects of high ambient temperature load capacity of bearings based on Hertzian stress limittions. Potentially serious thermal de formation effects in non-iso-expansive structures are also briefly examined. Temperature constraints on the sizing of actuators are discussed, based on the allowable maximum temperatures of motor windings. It is concluded that these constraints are manageable provided they ae recognized sufficiently early in the design process and some design guidelines for dealing with them are presented.

凹凸路面における動的2足歩行の制御について

This paper introduces a control method for biped walking on rugged terrain. We assume a biped robot which has a mass body and massless legs, and which is restricted to move in a vertical plane. We apply constrain control to the body of the robot so that it moves on a particular straight line and rotates at a constant angular velocity. As the result of such control, the dynamics of the center of mass of the body becomes completely linear. We also notice that the dynamics of the body does not depend on the slope of the line on which the center of mass of the body is constrained. We call such motion of the ideal model “Linear Inverted Pendulum Mode”. The limitation of the condition under which this method works is also discussed.After these consideration, we develop the control scheme of the biped walking on rugged terrain. Under the control based on the linear inverted pendulum mode, walking on a particular rugged terrain is shown to be equivalent to walking on a level surface.Finally, it is shown that by using ankle torque, our method is robust and can be applied to a real biped robot with mass legs. That is ascertained by simulation.

Motion and Structural Response of a Hydroelastic Semi-Submersible Model to Waves and Ice Impacts

This paper presents the motion and structural responses of a model that is structurally and dynamically similar to a typical semi-submersible platform. The model is fabricated of high impact polystyrene sheets, 0.78 mm (0.03 in.) thick, and cellulose acetate butyrate (CAB) tubes (for bracings), 1.58 mm (0.06 in.) thick. The response of the model to regular and irregular waves under operating/survival conditions and impacts of modeled bergy-bits (prototype weights of 1000 t and 2000 t traveling at speeds of 1.0 to 4.0 m/s) was determined. In addition, the response of a damaged-corner-column semi-submersible to survival wave conditions was also examined. The motion and structural responses were monitored using 30 strain gages, an accelerometer and four potentiometer devices. The impact loads were simulated by weights swinging in a pendulum mode in still water. The motion RAOs, stress RAOs, PSDs of stresses, impact loads versus time histories, etc., are computed and compared with published values. There is a very good agreement between the present experimental/analytical results and other results published earlier for the motion response. It was found that the theoretical models tend to overestimate the structural response at short wave periods and underestimate it at long periods.

Spectral analysis of gapped data: Search for mode 1S1 at the South Pole

The exigencies of operating an ultralong‐period seismometer/gravimeter at the South Pole have obliged us to search for evidence for the pendulum mode of the earth's inner core as a signal with poor signal‐to‐noise ratio, recorded with lengthy interruptions in the time series. In our method for identifying a weak, almost harmonic time signal in the presence of record gaps, we assume the signal is phase coherent for the full time series across the gaps and perform Fourier analysis of the full data sequence. The signal‐to‐noise ratio is improved by 1/(M)1/2 over the case where individual gapped segments are summed, where M is the number of segments. Analysis of the recordings from the South Pole both before and after the Sumbawa earthquake shows no spectral line identifiable with the pendulum mode that is above the noise level.