Simulation of Low Gravitational Field Using Gravitational Offloading and Force Control

For space exploration missions it is important to understand the behavior of a rover or astronaut under reduced gravitational field of the targeted planetary body. Since testing is an integral part of any mission, the simulation of low gravity is important although challenging under earth condition with relatively much higher gravitational forces than those of small bodies. The current paper focuses on simulating low gravitational field of planetary bodies by the method of offloading additional gravitational force by the method of suspending a counterweight in which the difference of masses will result in the required gravitational force (G- force). The dynamic motion of the test subject will be countered by a brushless dc motor to keep the required G- force. The modelled system is transformed into frequency domain to obtain the transfer function for the complete control system. The designed controller includes an inner velocity control loop that controls the motor and an outer force control loop to generate the required gravitational forces and to keep the system stable.