Masatsugu Otsuki

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.

This report deals with a rock-crasher embedded in the science integrated package for future lunar exploration. The crusher measures 59×60×129 mm and weighs 490 g. The generative impact force and consumption power were 150 N and 6 W at a voltage of 24 Vp-p and a driving frequency of 50 Hz device. A tool bit with pyramids driven with a solenoid was made from tungsten carbide. When a basalt sample was randomly fed with a feedscrew and crank mechanism in two directions, a smoothed surface was obtained. Ridges remained in one direction feeding even by skewing the tool at an angle of 11.4&deg.

This report deals with the machining performance of rock samples in vacuum with a rock-crasher embedded in the science integrated package for future lunar exploration. A tool bit with pyramids driven with a solenoid was made from tungsten carbide. The generative impact force was 150 N at a driving frequency of 50 Hz device. The machining amount in vacuum was smaller than that in air because debris adhered on the tool by electrostatics. The tool temperature rose 4°C while the solenoid temperature rose 48°C.

In future lunar, planetary or asteroid explorations, in-situ analysis of rock samples are strongly demanded to obtain many data from various aspects. For precise composition analysis, a sample surface should be smoothed. In this report, a surface shaver with a piezoelectric actuator is proposed and its machining performance in air is investigated. Shaving teeth are mounted at the ends of a lever mechanism. The device is pressed through four springs onto the specimen with a linear actuator. When a sinusoidal voltage of 50 Vp-p and an offset voltage of 25 V ware applied, the natural frequency was 556 Hz and the unloaded amplitude of shaving teeth were 0.77 mmp-p. Basalt samples were machined for 10 minutes in air. The surface roughness was small with an increase of the pressing force. However, the removal amount was smaller with an increase of the pressing force further. The surface roughness varied widely not only due to removal amount but also due to pores.

JAXA is developing a mobile rover to lunar surface exploration or base construction as a follow-on KAGUYA. Because the lunar surface is covered by regolith, implying an irregular and rough terrain, the rover has difficulty in mobility. Therefore a new low-pressure wheel is recommended for high mobility performance and low power consumption. A low-pressure wheel can change its contact shape and pressure distribution to account for terrain. In this paper, the measurement of shear modulus for low-pressure wheel on the deformable terrain is presented. This procedure is valuable for rover turning analyzing with a low-pressure wheel on the deformable terrain.

Supposing a space mission of setting monitoring devices at suitable positions on the moon, we discuss how to apply a casting manipulation to the mission. This paper addresses a control method to launch a penetrator to the desired position. First, we focus on a method by using rotation of a boom, and then introduce the mechanism that keeps a posture of the penetrator equipped at the tip of the boom constant for the absolute coordinate system during its rotation. This mechanism prevents the wire which connects the penetrator and the robot's base from winding the boom. Analyzing a position error of landing point caused by delay of releasing the penetrator and control error of the boom, we propose the motion control of the boom to reduce the error. Finally, we verify the effectiveness of the proposed method through experiments.

JAXA is developing a mobile rover to lunar surface exploration or base construction as a follow-on KAGUYA. Because the lunar surface is covered by regolith, implying an irregular and rough terrain, the rover has difficulty in mobility. Therefore a new low-pressure wheel is recommended for high mobility performance and low power consumption with a less complex mechanism. A low-pressure wheel can change its contact shape and pressure distribution to account for terrain. In this paper, the procedure for the measurement of mobility parameters like contact pressure on the deformable terrain, and a contact mobility model for low-pressure wheels are presented. This measurement is valuable for analyzing the interaction between a low-pressure wheel and the deformable terrain.

Supposing a space mission of setting monitoring devices at suitable positions on the moon, we discuss how to apply a casting manipulation to the mission. This paper addresses a mechanism of a casting manipulator system and control method to launch a penetrator to the desired position. First, we classify launching methods, and focus on a method by using rotation of a boom. We then propose the mechanism that keeps a posture of the penetrator equipped at the tip of the boom constant for the absolute coordinate system during its rotation. This mechanism prevents the wire which connects the penetrator and the robot's base from winding the boom. Analyzing a position error of landing point caused by delay of releasing the penetrator, we propose the motion control of the boom to reduce the error. Finally, we develop the system and verify the effectiveness of the proposed method.

On the landing of a spacecraft, a large shock load leads to undesirable responses, such as rebound and trip. The authors have discussed the control problem of these shock responses by momentum exchange impact dampers (MEIDs). The optimal design parameters of MEIDs for the landing of a spacecraft are investigated. The parameters are crucial for applications of MEIDs. This paper discusses the parameters of MEIDs with single-axis falling type problem, which is the most fundamental problem. It is found that the rebound height is proportional to the mechanical energy of the spacecraft. Thus, the optimal design parameters of the MEIDs correspond to the parameters that minimize the mechanical energy. Then, in order to improve the performance of the MEIDs, a novel MEID - HMEID (Active/Passive-Hybrid-MEID) has been proposed. The HMEID combines actuators with passive elements such as contact springs. Based on the optimal design result of the MEIDs, a stiffness control is applied to the HMEID in order to suppress the mechanical energy further. Simulation studies reveal that the HMEID can effectively reduce the influence of shock responses. The robustness of the HMEID against the stiffness of the landing ground is shown. The feasibility of the HMEID is also discussed. The effectiveness of the HMEID is superior to that of PMEID, even if the actuator has a dynamics with a large electric time constant or force constraint.

JAXA is developing a mobile rover to lunar surface exploration or base construction as a follow-on KAGUYA. Because the lunar surface is covered by regolith, implying an irregular and rough terrain, the rover has difficulty in mobility. Therefore a new low-pressure wheel is recommended for high mobility performance and low power consumption. A low-pressure wheel can change its contact shape and pressure distribution to account for terrain. In this paper, the procedure for the evaluation of drawbar pull calculated by shear stress on the deformable terrain is presented. This procedure is valuable for analyzing the interaction between a low-pressure wheel and the deformable terrain.

In this paper, a comprehensive wheel model for both flexible/rigid wheels driving on deformable terrain is developed. The wheel model exploits a terramechanics-based approach with taking account of pressures generated by wheel elasticity as well as terrain stiffness. Deflection of a (semi-) flexible wheel depends on a relative pressure between the wheel and terrain: the wheel will be significantly deformed on rigid terrain whereas it will be hardly/slightly deformed on soft terrain. The wheel-terrain interaction in the proposed model is divided into three contact sections: wheel front section, wheel deflected (flat) section, and wheel rear section. The stress distribution at each contact section is formulated, and then, the traction force of the wheel is obtained as an integral of normal and shear stresses generated at each section. Simulation studies with varied wheel pressures, such as flexible, semi-flexible, and rigid wheels, are conducted to validate the proposed model. Also, traction performances of flexible/rigid wheels are compared based on a metric called tractive efficiency. The simulation results provide an important finding in terms of an optimal wheel pressure of flexible wheel for better traction.

This paper presents the synthesis procedure of an input profile for a motion control system to simultaneously reduce sinkage and vibration in a planetary rover. The sinkage of the rover changes depending on the degree of a contact force against loose soils in surface of a planet. Through the experiments using the lunar regolith simulant, it is confirmed that the sinkage is largely concerned with acceleration and deceleration in a driving mechanism. Hence, we proposes the method to suppress the sinkage by appropriately designing the acceleration profile with an asymmetric shape. Moreover, the vibration due to flexibility of the wheel is induced by self-motion and we verify the vibration reduction using the command shaping method through the experiment. Consequently, this paper presents the easy design procedure of the acceleration profile and the valuable experimental results.

In the lunar-planetary exploration, most of landers made a landing on flat areas of surface, because there are a lot of rocks craters and hills on lunar-planetary surface. For the next generation lunar-planetary exploration, the development of a highly accurate landing technology is demanded to land on the complex terrain. The navigation-guidance technology and hazard avoidance have been studied for the safe landing. Moreover the development of landing leg is required for the safe landing in the final phase of landing sequence. This paper presents the development of experimental system of active landing leg, and examine the landing shock response. In addition, we consider the effectiveness of active landing leg and the application to the control method of lander's overturn prevention.

This paper proposes the synthesis procedure for the motion control system to reduce slippage in a planetary rover. The slippage in the rover is mainly due to degree of contact force against the loose soil on the planetary surface. In this paper, particularly, it is confirmed that the slippage generating in early phase of the rover motion is involved with acceleration and deceleration in the driving mechanism through the experiment. Hence, we propose the command shaping method of the target acceleration to prevent the increase of the slippage and the acceleration profile is then derived only by solving a regulator problem with an initial velocity and taking account of the maximum value in acceleration.

This paper describes an application of conventional terramechanic contribution to mobile robots or vehicles in rough terrain. Terramechanics, addressing the interactive mechanics between a vehicle and a terrain, has mainly affected machines for agriculture, construction or planetary exploration. However, it is not clear that wheeled locomotion is able to cope with a critical situation getting stuck into soil. So, the authors elaborate the application of established wheel models in terramechanics to discuss an avoidance capability of such situation. Further to this, different characteristics of a single wheel and a multi-wheeled robot are presented. In this paper the interpretation of the conventional studies and experimental remarks is noted based on simulation analyses.

This paper will propose a concept of onboard systems for command-planning, executing, and system monitoring that are commonly needed by autonomous remote systems. The concept will use an onboard script-engine by the help of a well-known three-layered approach consisting of deliberation, execution and driver layers to implement a command module to accept commands consisting logics such as functions as well as typical commands. In addition, a result of an experimental implementation onto a AUV (Autonomous Underwater Vehicle) will be presented followed by the discussion on the expression of plan of mission for autonomous systems.