This project studies the motion of a compact and highly mobile six-legged all terrain robot that rolls on wheels when possible, but can use the wheels as feet to walk when necessary. While gaited walking may suffice for most situations, rough and steep terrain requires novel sequences of footsteps and postural adjustments that are specifically adapted to local geometric and physical properties.
There is an enormous variety of walking robots in the world today. M ost of them have six legs to maintain good static stability, many have 8 legs for greater speed and higher load capacity and there are some that implement clever balancing algorithms which allow them to walk on two legs to move over sloping ground and to climb up and down stairs, like humans do (e.g. Such as Honda's Asimo robots). In general, the main motive behind the creation of most of these walking machines is to enjoy experiencing about the physics of motion by applying state of the art technologies to control the movement of articulated limbs and joint actuators. It would be beneficial for a mobile robot to possess the advantages of extreme rough terrain negotiating flexibility, which multi degree-of-freedom (M DOF) legs can offer, with the high-speed and simplicity afforded by wheels.
Basic Mechanism and Principle used:
Four bar linkage are the closed loop kinematic linkage, they perform a wide variety of motions with a few simple parts. This project discusses the design & fabrication of one such mechanism. In this project Six Leg Kinematic movement works on Grashoff's principle which states that the sum of the length of the shortest and longest links must be less than or equal to the some of the other two links.
However this condition is necessary but nor sufficient. Mechanism satisfying this condition will fall into crank-rocker mechanism, double crank mechanism and double rocker mechanism. A frame, connecting rod, crank & a lever constitute to obtain the required motion. In this project we tried to show mainly the application of simple four bar mechanism. It has following advantages. It is less expensive and maintenance is less. It can carry heavy loads and run on rough and uneven terrains.
A Hexa legged robot is a mechanical vehicle that walks on six legs. Since a robot can be statically stable on three or more legs, a hexa legged robot has a great deal of flexibility in how it can move. If legs become disabled, the robot may still be able to walk. Furthermore, not all of the robot's legs are needed for stability; other legs are free to reach new foot placements or manipulate a load. Wheels can be locked and used as feet to walk out of excessively soft, obstacle laden, steep, or otherwise extreme terrain.
In this project we trying to develop a different prototype base on the related principle so that a less expensive, easy to maintain, easy to handle and easy to deploy prototype can be available as a strong component of previously developed robotic systems.
Six leg mechanical spiders have a wide range of application in the manufacturing of robots. It can also be used for military purpose. By placing bomb detectors in the machines we can easily detect the bomb without harmful to humans. It can be used as heavy tanker machines for carrying bombs as well as carrying other military goods. It is also applicable in the goods industries for the small transportation of goods inside the industry. The mountain roads or other difficulties where ordinary vehicles cannot be moved easily can be replaced by our six leg mechanical spider. The geometry and conditions can be changed according to application needs.
So footfalls are the ³bottleneck´ of any motion – if we can find two subsequent transitions, it is likely we can find a path between them. This statement has been verified in our experiments.
We implement our planner using an approach similar to the previously explained one that combines graph searching techniques to generate a sequence of candidate footfalls with probabilistic sample-based planning to generate continuous motions to reach them. But several key tools embedded in this framework are tailored specifically to athlete.
We need a method of sampling feasible configurations (from scratch as well as via perturbation) and of connecting pairs of configurations with local paths, hard since athlete has many degrees of freedom and many closed-loop chains. We also need a heuristic to generate footfalls and to guide our search through the collection of stances, hard since lunar terrain is difficult (so careful selection of footfalls is important) but not extreme (so the number of candidate stances is enormous).
Finally, we need to smooth athlete‘s motion both to look natural when interacting with a human operator – hard since the robot is not anthropomorphic – and to help avoid disturbing the ground (for example, by toppling rock). Simulation results will demonstrate the viability of our approach. We also show the flexibility of our implementation by adapting it to rappelling as well as walking motions of our prototype.
Walking robot is the leg and wheel hybrid mobile robot that can walk and also can roam also. Now many studies have been done about leg-wheel hybrid mobile robot, but most of them attaches active wheels, wheels driven and steered by electric motor. But installation of active wheels greatly reduces the mobility of walking machine, because they are usual heavy and bulky. Proposed hybrid mobile robot is a vehicle with a special foot mechanism, which can be changed from the sole of the walking vehicle to passive wheels for wheeled vehicle by the mechanism shown in shows the trajectory of the foot and the body in roller walking
Mechanical Design and Auto Cad Design
The mechanical design of the wheel unit One of the most important points of the wheel unit is pseudo-multi-DOF driving mechanism. It is to use only two main driving motors and five braking mechanisms to drive five joints in a psudo-5-DOF motion. The arm has active shoulder joint, elbow joint, wrist joint, and a gripper. The arm can also be rotated around the wheel axis. Therefore when the wheel unit is in ³locomotion mode´, the wheel can move around on the ground with high mobility. In this propulsive motion, the arm is used to sustain reaction moment generated by the propulsive motion of the wheel rotation by pressing the arm against the ground. To reduce the friction of the arm against the ground, a caster is
Submitted by hardik