To investigate the effect of localizing flexibility on locomotion speed, experiments were performed using an MR-DF and an MR-LF of equal mass (2.55 g). In each experiment, the robot was placed in a confined channel and actuated by a rotating actuator magnet at a vertical offset ya relative to the robot’s initial position (x = 0, y = 0; see Figure 1D). Rotation of the actuator magnet (ω = 2 Hz) induced body bending, causing the robot to take steps at the same frequency and move in the +x direction (see sign convention in Figure 1D). A range of ya values was studied because existing literature reported a relationship between ya and locomotion.(Pham et al., 2020)
Results show that the average initial speed (average speed for the first ten steps of locomotion) of MR-LF was faster than the MR-DF control at every y
a offset (see Figure 1F). At y
a = 11 cm, the robots had the closest speeds (difference of 3%) and exhibited their fastest average initial speed (MR-DF: 6.61 mm/rev, MR-LF: 6.82 mm/rev). The largest difference (299%) and slowest average initial speed for both designs were at y
a = 15 cm (MR-DF: 0.34 mm/rev, MR-LF: 1.37 mm/rev). As anticipated, the closeness
[YLK3] [TG4] in robot speeds is likely due to the comparable foot flexion between the designs (0% difference in minimum, 10% difference in maximum foot flexion). The superior performance of MR-LF, which had an average initial speed of 0.21 to 2.27 mm/rev faster than MR-DF across all y
a, may be due to ann expected difference in mass distribution between the robots or from the 10% reduction in maximum foot flexion. The closeness in locomotion performance between the MR-DF and MR-LF designs, and the superiority of MR-LF across all y
a is exciting because it demonstrates that localizing flexibility yielded a 3-299% increase in speed while also freeing up space for an internal compartment (308 mm
3) for functional integration.
In the experiments, the robot’s motion in the +x direction (i.e., away from the actuator magnet) was intended to demonstrate its ability to move in a less-favorable direction, as performed
[YLK5] [TG6] in previous work.(Steiner et al., 2022) In practice, robot speed and endurance can be improved by having the robot travel toward the actuator magnet and actively modulating the separation between the actuator and robot.
[YLK3]can you replace ‘similarity’ with other terms – ‘closeness/ %?)
to be confuse with “Similarity” in science (e.g. fluid)
[YLK5]replace this – performed?