Yohei Kushida

Robust Landing Gear System Based on a Hybrid Momentum Exchange Impact Damper

When a spacecraft lands, a large shock load can lead to undesirable responses such as rebound and tripping. The authors previously discussed the problem of controlling these shock responses using momentum exchange impact dampers. An active/passive hybrid momentum exchange impact damper, which included an active actuator, was proposed. The momentum exchange impact dampers’ performances are evaluated by the maximum rebound height, which is proportional to the mechanical energy of the spacecraft. However, the time responses of the energies have not been explained. In addition, the effectiveness of momentum exchange impact dampers was evaluated only in a one-dimensional motion simulation. This paper includes theoretical analyses, simulation studies, and experiments. The time responses of the energies of momentum exchange impact dampers are discussed. This paper proposes a robust landing gear system for spacecraft using a hybrid momentum exchange impact damper and evaluates its robustness against ground stiffn...

Experimental Study on Vibration Control of Flexible Structures Taking Power Assisted Conveyance Into Account

Abstract Power assist devices have been introduced to reduce physical burden of workers in conveying and mounting work in industries. Most of them handle controlled objects as rigid bodies. This paper discusses an effective vibration control method for conveying flexible structures with power assist. In this study, the power assist is realized by an impedance control method. The impedance characteristics of the power assisted object correspond to the dynamic characteristics of the disturbance for the vibration control. Our previous paper discussed a disturbance accommodating LQ optimal control (DAOC) method for the vibration control problem and the effectiveness was verified by state feedback control simulations only. In this paper, the DAOC method is applied to the same cart with a 1-DOF vibration system as in the previous paper but having more flexible structure. The natural frequency of the controlled object is set to 1.0 Hz. The effectiveness of DAOC in this case is demonstrated through actual experiments on the basis of output feedback control implementation.

Fundamental Study of Momentum-Exchange-Impact- Damper-Based Robust Landing Gear

When a spacecraft lands, a large shock load can lead to undesirable responses such as rebound and tripping. The authors previously discussed the problem of controlling these shock responses using momentum exchange impact dampers (MEIDs). An active/passiveHybrid-MEID (HMEID), which included an active actuator, was proposed, and stiffness control was applied. The stiffness control method controls spring coefficient between the damper mass and the body mass. The MEIDs’ performances are evaluated by the maximum rebound height, which is proportional to mechanical energy of the spacecraft. However, the time responses of the energies have not been explained. In addition, the effectiveness of MEIDs was evaluated only in a one-dimensional motion simulation. This paper includes theoretical analyses, simulation studies, and experiments. The time responses of the energies of MEIDs are discussed. This paper proposes a robust landing gear system for spacecrafts using HMEID and evaluates its robustness against ground stiffness variation. In this paper, MEIDs are applied to a mass-damper-spring-model, which takes ground viscosity into account. Effectiveness of the proposed model is verified by simulations and some experimental results. Nomenclature c c = contact damping coefficient of the damper mass, N ⋅ s/m d c = damping coefficient of the MEID spring, N ⋅ s/m f c = damping coefficient of the soil, N ⋅ s/m fg c = damping coefficient of the linear guide, N ⋅ s/m ) (t Fa = thrust force of the actuator, N rg

Momentum exchange impact damper design methodology for object-wall-collision problems:

Momentum exchange impact dampers (MEIDs) were proposed to control the shock responses of mechanical structures. They were applied to reduce floor shock vibrations and control lunar/planetary exploration spacecraft landings. MEIDs are required to control an object’s velocity and displacement, especially for applications involving spacecraft landing. Previous studies verified numerous MEID performances through various types of simulations and experiments. However, previous studies discussing the optimal design methodology for MEIDs are limited. This study explicitly derived the optimal design parameters of MEIDs, which control the controlled object’s displacement and velocity to zero in one-dimensional motion. In addition, the study derived sub-optimal design parameters to control the controlled object’s velocity within a reasonable approximation to derive a practical design methodology for MEIDs. The derived sub-optimal design methodology could also be applied to MEIDs in two-dimensional motion. Furthermore, simulations conducted in the study verified the performances of MEIDs with optimal/sub-optimal design parameters.