This paper introduces jumping robots as a means to traverse rough terrain; such terrain can pose problems for traditional wheeled, tracked and legged designs. The diversity of jumping mechanisms found in nature is explored to support the theory that jumping is a desirable ability for a robot locomotion system to incorporate, and then the size-related constraints are determined from first principles. A series of existing jumping robots are presented and their performance summarized. The authors present two new biologically inspired jumping robots, Jollbot and Glumper, both of which incorporate additional locomotion techniques of rolling and gliding respectively. Jollbot consists of metal hoop springs forming a 300 mm diameter sphere, and when jumping it raises its centre of gravity by 0.22 m and clears a height of 0.18 m. Glumper is of octahedral shape, with four 'legs' that each comprise two 500 mm lengths of CFRP tube articulating around torsion spring 'knees'. It is able to raise its centre of gravity by 1.60 m and clears a height of 1.17 m. The jumping performance of the jumping robot designs presented is discussed and compared against some specialized jumping animals. Specific power output is thought to be the performance-limiting factor for a jumping robot, which requires the maximization of the amount of energy that can be stored together with a minimization of mass. It is demonstrated that this can be achieved through optimization and careful materials selection.

https://iopscience.iop.org/article/10.1088/1748-3182/2/3/S01/pdf

Jumping robots: a biomimetic solution to locomotion across rough terrain

This paper proposes a new mobility system for planetary rover using springs and linear actuators. In the microgravity environment, hopping mobility is a possible choice for enhancing a new mobility of the robot. One method to hop is to press one's own to the ground. The proposed robot consists of two masses, and can press one's own to the ground using springs. So the rover can hop from the stationary state by transforming the elastic energy to the kinetic energy using the springs and linear actuators. Furthermore the robot can land without bounding by transforming the kinetic energy to the elastic energy. The simulation studies and the ground experiments shows that the proposed rover could hop and land.

New mobility system based on elastic energy under microgravity

Mobile robots for rough terrain are of interest to researchers as their range of possible uses is large, including exploration activities for inhospitable areas on Earth and on other planets and bodies in the solar system, searching in disaster sites for survivors, and performing surveillance for military applications. Nature generally achieves land movement by walking using legs, but additional modes such as climbing, jumping and rolling are all produced from legs as well. Robotics tends not to use this integrated approach and adds additional mechanisms to achieve additional movements. The spherical device described within this thesis, called Jollbot, integrated a rolling motion for faster movement over smoother terrain, with a jumping movement for rougher environments. Jollbot was developed over three prototypes. The first achieved pause-and-leap style jumps by slowly storing strain energy within the metal elements of a spherical structure using an internal mechanism to deform the sphere. A jump was produced when this stored energy was rapidly released. The second prototype achieved greater jump heights using a similar structure, and added direction control to each jump by moving its centre of gravity around the polar axis of the sphere. The final prototype successfully combined rolling (at a speed of 0.7 m/s, up 4° slopes, and over 44 mm obstacles) and jumping (0.5 m cleared height), both with direction control, using a 0.6 m spherical spring steel structure. Rolling was achieved by moving the centre of gravity outside of the sphere’s contact area with the ground. Jumping was achieved by deflecting the sphere in a similar method to the first and second prototypes, but through a larger percentage deflection. An evaluation of existing rough terrain robots is made possible through the development of a five-step scoring system that produces a single numerical performance score. The system is used to evaluate the performance of Jollbot.

A biologically inspired jumping and rolling robot

In recent years, small body exploration missions have received a lot of attention. JAXA completed Hayabusa mission in 2010 and succeeded in getting samples from the asteroid. JAXA is also developing the Hayabusa2 spacecraft, the post sample return mission to a near-earth asteroid. A novel and tiny hopping rover called MINERVA was installed into Hayabusa spacecraft. Then, with these experiences, some rover packages are under development for Hayabusa2 spacecraft. The mission concept is the same as MINERVA, but multiple rover system is introduced. Because the target asteroid parameters may be different from the previous target in Hayabusa mission, the rover system is newly designed in Hayabusa2 mission. This paper describes the challenge of mobilizing a robotic probe for small body surface exploration. This paper proposes a hopping mechanism and shows the effectiveness of the proposed hopping robot by micro gravity experiments. This paper also discusses the required intelligence for small body exploration robot.

Intelligent rover with hopping mechanism for asteroid exploration

Performance of mobility is highly dependent on the gravitational environment. Some researchers have proposed novel locomotion methods for extremely small terrestrial bodies like asteroids. Hopping is a possible method under micro-gravity. It is not proved, however, that the proposed method of locomotion is optimum for a given level of gravity. The purpose of this paper is to analyze which level of gravity is optimum for each mechanism, and which mechanism or parameter is optimum for each level of gravity. First, a classification of locomotion mechanism is described. Next, the speed of hopping and wheeled robots is compared. Finally, some simulation studies are performed to analyze the detailed mobility of wheeled robots.

A study of locomotion mechanism based on gravitational environment

A new type of mobility is discussed for space projects such as the MUSES-C aiming at small asteroid exploration. We propose the use of electro-magnetic levitation in order to integrate a mobility into the microgravity rover. The rover has a spherical shape and a smaller spherical shell inside. Four electromagnets are symmetrically located between the outer sphere surface and the inner sphere shell with one end of each directed to the center of the shell. With electromagnetic force of the magnets, a sphere iron ball inside the shell is controlled and levitated. When the rover lifts the ball inside with the electro-magnetic force, the rover is in return pressed down the ground by the reaction force, due to which the rover system not only gains upward momentum for floatation, but also obtains friction that enables its rolling on the ground. The prototype microgravity rover was developed and experimental results indicate effectiveness of the proposed mobility.

S. Shoji

Papers

Mobility of a microgravity rover using internal electro-magnetic levitation