Modify a wheelchair into 2 DoF system to enable patient feels less shaking (vibration impact) when moving over a playground rough surface.
Modify the structure into a 2D spring and mass vibration model.
Search from the product catalogues to get actual values of elastic stiffness for the wheels or spring stiffness in you 2 DoF model.
Illustrate the modal forms of vibration.
If to install a vibration absorber, determine the optimal operating frequency when the wheelchair is used to carry 160 kgf weight of patient.
The operating frequency has to be >20% between the 2 natural frequencies.
Justify your design to convince the hospital on how the wheelchair is comfortable when carrying a patient.