For a mechanism with many elements that needs to be shaking-force and shaking-moment balanced with a low addition of mass, a low addition of inertia, and a low addition of complexity, the use of actively computer-controlled balancing elements is promising. With these actively controlled elements the net reaction forces and the net reaction moments to the base of the mechanism can be balanced directly instead of balancing each mechanism element separately as is common practice for passive balancing. Adaptability of the control also allows balancing of (variable) payload. This paper presents the concept of an active dynamic balancing unit, which is a unit that is mounted on unbalanced mechanisms and is controlled such that the combined system is dynamically balanced. The conceptual design and possible control strategies of such a unit, including pick-and-place motion of variable payloads, is studied. A simulation is presented to give insight in the possibilities and limitations of active dynamic balancing.