大槻 真嗣

Next-generation lunar/planetary exploration spacecraft need to solve problems of conventional landing methods and mechanisms such as high rebound, impossibility of reuse and high cost. For this purpose, the authors discuss the landing method by means of Base-Extension Separation landing Mechanism (BESM) which uses energy conversion with springs and separable units. In the authors' conventional studies, its effectiveness was confirmed for a simple case based on single-axis restriction. However, the investigation of tumble prevention cannot be treated in the simple case. The purpose of this preliminary report is the response analysis of a slope landing case of BESM for more practical landing situations.

This paper presents the influence of shadow on the path planning of lunar rovers. To evaluate the influence of shadow, the terrain and shadow on the Moon are first modeled using the DEM derived from Kaguya data. Subsequently, on the basis of a path planning algorithm considering the shadow, numerical simulation is performed for the lunar terrain. In the simulation, a short path crossing shadow is compared with a long path avoiding shadow under various insolation conditions. The simulation results confirmed that although avoiding shadow adds a traveling distance and time, it doses not much affect the average power consumption but contributes to an increase in the average power generated.

This paper presents the control method for vibration due to rotational motion of a casting manipulator . The casting accuracy for bringing an end-effector to a target position, which is attached to the odd end of a wire rotated by the casting manipulator, significantly depends on the attitude at the release time. Further, the attitude of the casting manipulator is horizontally and vertically vibrated by the rotational motion if the rotational axis does not coincide with the position of the gravitational center of the rotated arm; consequently, the considerable casting error occurs. Hence, this paper mentions the vibration problem of the casting manipulator; first, we confirm the stationary and non-stationary vibration experimentally; second, the casting error due to attitude shift is numerically analyzed; finally, the active vibration control method using an actuator is proposed. The vibration reduction due to the shift in yaw angle is particularly verified through the numerical calculation and the effectiveness of the active feedback and feedforward control is shown.

This paper presents the control method for vibration due to rotational motion of a casting manipulator. The casting accuracy of an end-effector, which is attached to the odd end of a wire rotated by the casting manipulator, significantly depends on the attitude at the release time. Further, the attitude of the casting manipulator is horizontally and vertically vibrated by the rotational motion if the rotational axis does not coincide with the position of the gravitational center of the rotated arm; consequently, the considerable casting error occurs. Hence, this paper mentions the vibration problem of the casting manipulator; first, we confirm the vibration experimentally; second, the casting error due to attitude shift is numerically analyzed; finally, the active vibration control method using an actuator is proposed. The vibration reduction due to the shift in yaw angle is particularly verified through the numerical calculation and the effectiveness of the active control is shown.

Moon holes were first discovered in the world by JAXA in 2009. It is believed that moon hole is helpful to know the formation of the moon because bedding plane is exposed. In addition, because inner hole is sealed from solar wind, it is also important as a candidate site for base camp in the future. However, exploration of the moon hole is difficult with the conventional robots. A new robot is required for going down and explore moon hole. In this study, a system to throw a small robot into a moon hole with wire is proposed. The author describes modeling and attitude control in a state where the robot is hanging by a wire, and evaluates the effectiveness of the system.

The development of highly accurate landing technology is required for the next generation lunar-planetary exploration lander to touch down on rough but interesting area. For the safe landing, the development of landing leg is required to prevent overturning and reduce landing impact of the lander in the final phase of landing sequence. However, it is difficult to design a landing leg which is applicable to a wide variety of terrain. The active landing leg is proposed as a solution of solving this problem. This paper presents the simulation of the lander with active landing leg and development of experimental system using Magneto-Rheological damper, and examines the landing shock response and penetration of the lander leg to the sand terrain.

This paper presents a technique for driving a wheel to control the sinkage of a planetary rover on loose soil. Dynamic sinkage of the wheels of the rover always occurs when it travels on loose soil in the planetary surface; sinkage is then caused by the soil deformation due to a compressive force generated by the wheel and the soil conveyance due to slippage in the wheel. When the wheel is driven in an acceleration profile with a trapezoidal shape, it is experimentally confirmed that the depth of sinkage changes during both acceleration and deceleration. Further, it is also confirmed that the terminal sinkage is proportional to the magnitude of the maximum rotational acceleration and deceleration of the wheel; consequently, we propose the method of controlling the sinkage by adjusting their magnitude. The proposed control is verified through the experiments using the single wheel test bed and the full body rover with 4 wheels; thus, it is confirmed that twofold increase of sinkage is caused and the terminal sinkage is controlled, especially suppressed.

We propose the method to control landing position and speed of an end-effecter in the air by multidirectional tension of wires. The end-effecter is connected with both dummy weights and reel system via the wires. After launching the end-effecter and dummy weights, its trajectory is changed by each tension of the wires when their motion is geometrically constrained. We develop the motion planner which makes the end-effecter reach the target at a suitable speed, and control algorithm for it. The proposed method is applied to the soft landing of the end-effecter. The effectiveness of the proposed method is verified through the experiment.

In 2009, the Selenological and Engineering Explorer (SELENE, nicknamed Kaguya) discovered a vertical hole of 〜60 m diameter and 〜50 m depth in the Marius Hills region on the Moon. After the discovery of the Marius Hills Hole (MHH), two other more gigantic holes were discovered by a global survey executed by the SENENE team. The vertical holes were likely formed by volcanic activities or tectonic processes such as skylight formation on lava tubes, from the terrestrial analogues. The indicative evidence of the existence of subsurface void spaces associating with the holes was indeed acquired by the US LRO later. Similar vertical holes have been discovered on the Mars. Various important knowledge of science on the Moon, the solar system, and extra-terrestrial life will be obtained by direct in-situ explorations into the lunar holes and their associating subsurface void space. However, the exploration of the holes and underlying subsurface voids require a system with the state of art which can overcome difficulties, such as the descent into the floors of the holes studded with boulders and the travel into the dark void spaces hidden from the lunar surface. We have studied on the exploration system by applying space robotics technology. We report the exploration system design, operational scenario in this paper.

The JAXA lunar orbiter spacecraft "SELENE (Kaguya)" found a vertical cave on the surface of the moon. For underground exploration of the moon, we propose the method to launch the probe vehicle into the cave by casting manipulator system. For the first step, we develop the launcher system which can generate kinetic energy of the end-effecter by rotating the boom and throw it to the target. We then verified that the system can throw the end-effector more than 17 meters and its positioning accuracy is less than 3.4% through experiments.

This paper addresses a method of releasing a penetrator during a boom's rotation to improve the precision of the position when its landing First, we point out the disadvantage of using the electromagnetic release device from a viewpoint of response variation We then propose a mechanical release device which is activated by collision between a release-lever equipped on the boom and a stopper set at the pillar of the system A gripping device based on the toggle mechanism is also proposed to hold the penetrator tightly against an excessive centrifugal force when the boom rotates at a high speed Developing these proposed devices, we finally conducted experiments of releasing the penetrator and analyzed a position error of its landing point We verified the effectiveness of the proposed method by showing that the error is less than 3% of the distance to the launching point through the experiments

Estimating a robot's own position is an essential requirement for autonomous mobile robots. Visual Odometry (VO) can play a key role in navigation tasks in slippery natural terrain, which highly degrade the accuracy of Wheel Odometry, without relying on other infrastructures nor any prior knowledge. A challenge of VO system lies in how to increase the number of features tracked between continuous frames in untextured terrain. Although there has been many feature selection algorithms proposed, none of them are sufficient in terms of calculation speed and robustness. Hence, this paper propose an algorithm that dynamically switches between high-speed/low-accuracy and low-speed/high-accuracy algorithm according to the texture of terrain. Validity of this algorithm was proved by the simulation using datasets taken at Izu-Oshima, Japan.