2.4. Effect of robot mass on speed

To investigate how the increased mass of functional components and payloads within the compartment affects locomotion speed, experiments were performed using MR-LF with varying mass (2.55, 2,87, 3.5, 4.43 g). Comparison between plots shows that, in general, increasing MR-LF mass increases the initial speed at smaller ya values and lowers the initial speed at larger ya values within the studied ya range (Figure 3A). At the smallest offset (ya = 9 cm), the heaviest MR-LF (4.43 g) exhibited the fastest average initial speed (9.01 mm/rev), while the other MR-LFs were unable to exhibit sustained locomotion (discussed in the next section). Conversely, at the largest offset (ya = 15 cm), the heaviest MR-LF (4.43 g) exhibited low average speed (0.02 mm/rev), while the 2.55 g and 2.87 g MR-LFs had average speeds greater than 1.0 mm/rev. Our results have also demonstrated that MR-LF was able to achive locomotion even with a mass greater than existing capsule endoscopy devices (PillCamâ„¢ SB 3: 3.0 g, PillCamâ„¢ Colon 2: 2.9 g).(Medtronic, n.d., n.d.) Indeed, the heaviest robot in our experiments exhibited the fastest average initial speed (9.01 mm/rev), and results show that increasing robot mass can improve locomotion speed and change the ya for the fastest locomotion. To further investigate this mechanism, we study the effect of magnetic field strength on locomotion as described in the next section.
 [YLK1]I have not started the final review of this section onwards. Will do in Saturday if possible. Thanks!