A framework for modeling and control is introduced for robotic manipulators with a number of energetically self-contained semiactive joints. The control approach consists of three steps. First, a virtual control design is conducted by any suitable means, assuming a fully-actuated system. Then, virtual control inputs are matched by a parameter modulation law. Finally, the storage dynamics are shaped using design parameters. Storage dynamics coincide with the system's internal dynamics under exact virtual control matching. An internal energy balance equation and associated self-powered operation condition are given for the semiactive joints. This condition is a structural characteristic of the system and independent of the control law. Moreover, the internal energy balance equation is independent of the energy storage parameter (capacitance), which adds flexibility to the approach. An external energy balance equation is also given that can be used to calculate the work required from the active joints. A simulation example using a 3-dof prosthesis test robot illustrates the concepts.