This paper presents the design and optimisation of compliant nonlinear torsional springs by parametric finite element analysis. The springs are created based on a single B-spline curve, which exhibits a compact, lightweight, and simpler design than existing works. The spring is created by a combination of computational finite element analysis methods and optimisation algorithms that analyse and optimise spring designs. The models and methodology of spring creation are presented with results. The constant-torque spring was able to outperform the generic constant spring design in some aspects as well as cosine-torque spring which perform an outstanding output in term of output accuracy. This thesis explores a new type of nonlinear torsional spring with advantages above generic nonlinear torsional spring as well as difficulties, limitations and recommendations of the spring design method used.