A transtibial/transfemoral prosthesis is a two-link kinematic chain (thigh + shank) driven at the hip by the residual limb, with a microprocessor knee that regulates flexion damping. Joint angles here follow a simplified gait-cycle model:
φ(t) = (t·cadence/60) mod 1 // gait phase 0..1
θ_hip = A_hip · sin(2π·φ) + incline
θ_knee = max(0, A_knee(stiffness) · sin(2π·φ − π/2)²·swing(φ))
- Cadence — steps per minute, sets the gait-cycle frequency for both joints.
- Knee stiffness — the prosthetic knee's damping coefficient; higher stiffness reduces peak swing-phase flexion, mimicking a microprocessor knee resisting buckling.
- Stride length — scales the foot's fore-aft excursion per step.
- Ground incline — biases the hip's neutral angle to model walking up/down a slope.
Real powered prosthetic knees (e.g. microprocessor and myoelectric knees) use exactly this kind of phase-based angle scheduling, adapted in real time from sensor feedback, to reproduce a natural gait.