A Muscle-Driven Mechanism for Locomotion of Snake-Robots

Abstract

This paper presents the concept of muscle-driven locomotion for planar snake robots, which combines the advantages of both rigid and soft robotic approaches to enhance the performance of snake robot locomotion. For this purpose, two adjacent links are connected by a pair of pneumatic artificial muscles wherein an alternate actuation of these soft actuators causes a rotational motion at the connecting joints. The muscle-based actuated linkage mechanism, as a closed six-linkage mechanism, was designed and prototyped. The linear motion and force generation of the pneumatic artificial muscle was experimentally characterized using isotonic and isometric contraction experiments. A predictive model was developed based on the experimental data to describe the relationship between the force–length–pressure of the PAMs. Additionally, the muscle-driven mechanism was kinematically and dynamically characterized based on both theoretical and experimental studies. The experimental data generally agreed with our model’s results and the generated joint angle and torque were comparable to the current snake-like robots. A skx-link planar snake robot with five joints, five pairs of antagonistic muscles, and an associated pneumatic controller was prototyped and examined for simple movements on a straight-line. We demonstrated the muscle-driven locomotion of the six-link snake robot, and the results show the feasibility of using the proposed mechanism for future explorations of snake robot locomotion.

Dynamics and Computed-Muscle-Force Control of a Planar Muscle-Driven Snake Robot

“…where e m i ∈ R 3 is the unit vector along the muscle direction. In Equation (36), f m i is the magnitude of the actuation force of the muscle on the right side of the link {i}, which can be determined based on a predictive model that is developed and discussed in [59]. Note that the formula for only one of out four muscle forces acting on the given body is presented here.…”

“…The overall results are in the feasible range of contraction length of the PAMs. The computed-muscle-force controller determined the required force to be generated by the PAMs, which then was transformed into the controlled pressure based on the forcelength-pressure predictive model developed in our previous study [59]. The control inputs (i.e., the muscle forces) for the first 40 s of the simulated-time are shown in Figure 6.…”

“…In our previous work [59], an artificial-muscle-driven snake robot was introduced, which uses a series of antagonistic PAMs, assembled lateral to the joints, where alternate activation of the antagonistic muscles generate the internal body motion and consequently the external locomotion due interaction with its surrounding environment. Based on experimental and analytical studies and their characterizations, it was demonstrated that the kinematic and dynamic performances of the snake robots are comparable to the current state-of-the-art snake-like robots, and, in some aspects, even exceed them.…”

Snake Robot with Motion Based on Shape Memory Alloy Spring-Shaped Actuators

“…However, the complexity of the control of this kind of actuation system is a main drawback, as the position of the joints is not directly related to the angular position of the motor shaft [ 36 , 37 ]. The third class of robots implements the use of pneumatic and hydraulic actuators, which allow for nonrigid movements and provide a high capacity to manipulate objects; however, at the same time, this kind of robot requires the use of pumps, thus increasing their cost and difficulty of transportation [ 38 , 39 , 40 ]. The final class of robots implements non-conventional actuators, which can be implemented on the robot without the necessity of a transmission system, such as the parallel elastic actuator [ 41 ], hydraulically amplified self-healing actuator [ 42 ], and shape memory alloy (SMA) actuators [ 43 , 44 ].…”

Combined Soft Grasping and Crawling Locomotor Robot for Exterior Navigation of Tubular Structures

“…To achieve higher maneuverability while navigating complex shape structures, the recent advancements in soft robotics enhance the capabilities of robots by incorporating compliant and structurally deformable bodies that generate a higher complex motion compared to their rigid counterparts and adapt to different environments, tasks, while reducing the possibility of damaging the structures [11,12]. In particular, textile-based (fabrics) and pneumatic artificial muscles (i.e., McKibben actuators) are capable of providing a high load-to-weight ratio [4,13,14]. Despite many research efforts in soft robots' locomotion and grasping, two growing research areas in soft robotics, the combination of locomotion and grasping capabilities in one soft robotic platform has not been sufficiently studied [4,[15][16][17][18].…”