The objective of the experiment was to make a biomimetic jumping robot using simple materials which could jump as far as possible across a flat floor without touching it. The inspiration behind the design of the jumper is addressed in this report.
The outstanding athletic ability of a “froghopper” which may have evolved as an escape mechanism from predators has been an inspiration for making this jumping robot.1
Froghoppers, popularly known as spittlebugs which are around six millimetres in length, recorded hops that were as high as 700 millimetres. Velocities of up to 3.1 m/s during take-off are actually quite fascinating. Subsequently a force of about 400g is experienced by its body. 1
Even though froghoppers have short legs, it utilizes a leg locking mechanism for attaining such great leaps. They mainly use this kind of mechanism because direct muscle contractions cannot produce necessary force required for huge jumps in a short time frame. 1
Jumping mechanism in froghoppers: A brief idea
Jumping occurs mainly when the hind limbs are locked in their fully levated positions and is powered by delayed contractions of large trochanteral depressor muscles in the metathorax. 2
Contractions of huge trochanteral depressor muscles in the metathorax results in developing a certain amount of energy which is responsible for bending bends two bilaterally symmetrical pleural arches 2. An elastic internal structure stores the energy produced from contractions and an explosive extension of the hind legs is acquiredby releasing the stored energy in less than a millisecond. 3
A certain amount of muscle force is generated and stored before the jump. They attain this by pulling their hind limbs beneath their thorax and locking them up in that place. Depression of the trochantera about the coxae generates necessary thrust for a jump and the depression is acquired by critical movement of the hind limbs1. Before take-off, the hind limbs are elevated so that the femora is pulled in between the thorax and the middle legs. 3
Locking is achieved by the help of a protrusion present beneath the insect which engages with a ridge present on its hind limb. 1The legs are released once the froghopper achieves desired force resulting in a skyward leap. 11 per cent of its body mass is constituted by massive thoracic muscles which power the jump. The bug is able to accelerate and increase height of jump by positioning of the muscles in the thorax. 1
The froghopper has a bi-stable structure where it utilizes the energy stored, for moving the bi-stable structure from one position to a meta-stable position and releases its energy resulting in the bi-stable structure which looks like a cantilever beam in between two fixed supports to drift to another position which results in the explosive jump.
Fig 2: movement of hind legs and take-off in a froghopper3