Experimental Suspension for Wheeled Vehicles and Robots Aimed for Harsh and Off-Earth Environments

Experimental copper beryllium suspension consisting of 4 units (quasi-rocker arms) was designed for the Sirius II rover, created by Students' Space Association at Warsaw University of Technology. The aim was to create a suspension system for multi-purpose wheeled robot, that will be easy to manufacture, assemble and maintain, have no kinematic pairs, and fulfil the goal of absorbing shocks and vibrations, while traversing through rough and uneven terrain. Copper beryllium alloys have high fatigue strength, excellent wear and corrosion resistance, can operate in wide range of temperatures, from low cryogenic (-200°C) up to 250°C. The 3D model was created and then numerically analysed with the usage of Ansys Mechanical, with the static load based on the rover geometry and masses, collisions with different obstacles, dynamical load cases with eigenfrequencies values and many more. Based on the consecutive analysis, the design was optimised until the desired strength and deflection parameters were obtained and the safety factor fulfilled our needs ensuring that the structure will withstand standard operating conditions but will also cope with unexpected accidents or falls. Final structure has a look of a spring with 10 folds. Complex spring-like structure and subtle differences in radii on quasi-rocker arm folds resulted in that the part could not be manufactured by most manual methods, so from the beginning the preferred ones were computer controlled. Toxicity of beryllium was another factor considered and dismissed by manual manufacturing. In the end, the 23 mm thick plate of copper beryllium was introduced to the water jet cutter, which proved to be the most fitting method for this design cost- and quality-wise. After manufacturing, the suspension was mounted to the rover. Several tests were performed, among them - riding the plain and rocky terrain, riding up and down steep hills, pulling high masses (100 kg - with 45 kg rover total mass for comparison), collisions and abrupt change of load. The suspension performed perfectly well under every condition, ensuring great traction and stability for the rover without any sign of damage during and after continuous and extensive loads. Final design derived from student competition construction resulted in an innovative solution, which could be adapted in numerous vehicles for both Earth and other planets' environments, ensuring great traversal capabilities combined with relatively low-cost materials and low to no maintenance needs. Absence of kinematic pairs dismiss the need of lubrication and reduces material wear, while high-strength of used material lowers the risk of fatigue failure. Ability to operate in aggressive environments is also present, due to materials resistance to corrosion and chemical substances. Although simple, the proposed idea of design proved to be reliable and provides possibilities of further development to serve well in various wheeled vehicles in multiple types of harsh environments with rough terrains (off-Earth included).