Consider a one-armed robot which holds a swinging mass on a tether. The robot arm's base can swivel in the fx fy plane, making angle with fx. The arm has a pin joint at J, and the upper arm section can pivot about this joint to make angle with the fx fy plane. A mass M hangs from point H on the arm, forming angle with the vertical in the JH fz plane and angle in the plane perpendicular to this (see drawing). Values r1, r2, l are constant lengths. Values (t), (t), (t), (t) are variables. The masses in this setup are mJ at J, mH at H, and mM at M