There are kinds of soft manipulators that achieve appreciable performance in their specialty respectively, nevertheless, there isn’t a universal evaluation criteria for assessing and comparing their performance. In this page, aimed at reaching a high level of load bearing capacity with little loss in flexibility, we set these two characteristics as the main metrics.
Flexibility
As for flexibility, we define it as a manipulator’s reachable space, which consists of all the points that the tip of the manipulator can reach with another end fixed. To show comparison between manipulators with different shapes and scales, we calculate the ratio of that space to the dimensionality’s power of its original length, as a relative flexibility.
Minimum bending radius, original length, maximum length and width of the manipulator are represented as R, L0, L1 and D respectively. S1 is the bending arc and outer boundary and S0 is the bending arc and inner boundary.
Load bearing capacity
As for load bearing capacity, we define it as the maximum load moment of a soft manipulator when it is able to remain stable and its loaded end is on the same height with its fixed end. How the manipulator reaches such a condition is not confined.
F represents the internal force provided by the airbags, which is determined by the contact area S and pressure p. k1, k2, k3 represent the spring coefficients, M represents the load moment provided by this structure. To reach a balance, we assume a elongation of Δs for the springs.
The force balance can be represented as:
The load moment can be calculated as:
