Rocker Bogie Suspension System
The human body is a complex integration of intelligent parts in an intelligent way!
Have you asked yourself before why when you jump you don’t end of having a broken leg? Why your stomach and Kidney don’t leave their places permanently as a result of the shock? The answer simply lies behind “The Suspension Systems”. Every solid matter that exists on earth has its own fragility level. So, engineers have to reduce the shock forces on the bodies according to their strength.
Robot engineers are mined to bush their material to their limits, who doesn’t want a light and efficient robot! As they are reducing the material, their system tends to get weaker, to solve this issue they have to reduce the forces act on their systems; one of these methods is to add a suspension system/s to the moving or the sensitive parts, if you look at your body joints you will find a special tissues reduce and absorb the shock forces acting on your body, engineers have invented lots of suspension systems to overcome this problems and to protect their robots and vehicles.
A simple suspension system that everybody knows is the common car tires, these tires are made of strong rubber and filled with high pressure air, another common system is the spring system which usually reduces and delay our feeling of the sudden shock forces. Sometimes pneumatic or oil dampers are used. In lots of cases more than one suspension system is used in order to get a specific response from the system.
A very challenging application for suspensions is to apply it on a vehicle, specially a Space Rovers, usually space rovers are sent to another planet for exploration and scientific purposes, that requires a high level of safety and resistivity to the extreme hard terrain they may face. Otherwise, multimillion missions may end with fail which nobody wants. To reduce the shock forces on space vehicles engineers have invented a new suspension system called “Rocky Bogie Suspension” which is used in both Mars Exploration Rover (MER) and Mars Science Laboratory (MSL).
The Rocket Bogie system consists of two rockers (links) that are freely hinged to each other and to the main body, one of these two links is attached with an independent driving motor and wheel, the other link is bogie which links another two wheels with their driving motors. This system is on both sides of the vehicle so we will end with 6 wheels, each has its own driving motor. This system has lots of advantages; the right and left systems are independent and working separately; you can see the right wheel climbing while the left is descending. When the rover is climbs a high obstacle, first, the front wheel cross then the other two, sometimes the opposite; depends on the obstacle shape and dimensions. This system is giving a high level of stability to the center of gravity of the robot and provides it with high torque due to its six motors. Unlike your car suspension system, Rocky bogie system can enable the robot to climb an obstacle has twice its wheel diameter depends on the motor torque and wheel surface friction. Engineers have added lots of improvement to the simple Rocky Bogie system, some has added a spring after each wheel or just between the body and the rocky links, others have added torsion spring in the hinges to limit the rotation and help it attach to surfaces easily while climbing, others have added dampers to damp the sudden forces, another improvement is to give the rover the ability to change the angle between the links which will provide an optimum location for each situation and obstacle.
The efficiency of a suspension system is measured by its ability to reduce the forces on the body, distribute them wisely, keep the body stable and oscillates within the allowed limits and provide high oscillating angle which the robot can tilt without overturning. For Rocky Bogie system if the center of gravity is chosen accurately and wisely, it provides a high efficiency in each; as an example for a well-designed Rocky Bogie system, Curiosity Mars Rover which has an ability to tilt to 50 degrees without over turning.