Skip to main content
. 2015 Mar 11;113(10):3600–3609. doi: 10.1152/jn.00737.2014

Fig. 1.

Fig. 1.

A: multiaxis rotation system (MARS) balancing task. The left illustrates a participant in the MARS device holding with his right hand a joystick that controls roll motion (leftward deflection positive, rightward deflection negative). The MARS axis of rotation is indicated by the ⊗ on the right. The MARS direction of balance (DOB) could be offset from the gravitational vertical, and a DOB offset of +30°, left ear down, is illustrated. The MARS accelerates away from the DOB with an angular acceleration proportional to the sine of the angle φ between the chair axis and the DOB. When the MARS axis is between the DOB and the gravitational vertical, the MARS will move toward and past the gravitational vertical. B: schematic overview of the control hardware/software of the MARS device. The direction of balance could be offset relative to gravity by an angle that varied each trial. Variables fixed for the experiment included: joystick sensitivity (kJ = 12°/s at full deflection), pendulum constant (kp), and kinematic limits (φl = ±60°, φ̇l = ±300°/s, φ̈l = ±180°/s2). Variables updated every cycle of the software control loop include: angular position, velocity, and acceleration relative to the DOB (φ, φ̇, and φ̈); commanded angular position, velocity, and acceleration (φ^, φ̇^, and φ̈^); and angular position relative to gravitational vertical (φg). NI, National Instruments.