Design for load compensation

Many machines are intended to do work. While this may seem evident, for instance in lifting equipment, many machines consume significantly more energy than strictly required. Application of countermasses or countersprings has been shown to improve system behaviour in various situations, such as the elimination of resonance or operating force. Another reason to eliminate forces is to avoid vibrations to be induced in the machine or its environment.

The various methods that will be treated in this chapter can be distinguished in static balancing, dynamic methods, inertial match methods and active methods. Static balancing is a technique to create static equilibrium in a large range of motion rather than in a single position and is used to reduce operating force. Dynamic balancing is a technique to eliminate shaking forces or moments on the environment. Conversely, motion of the base does not affect a dynamically balanced mechanism. Inertial match methods play with the natural frequency in order to achieve resonance and thereby operating energy reduction for this state. Active methods make use of control systems to reduce the effect of disturbances. This is true of classical feedback loops, but also dedicated systems are included of actively moved countermasses to eliminate shaking forces and moments, either feedforward controlled or based on feedback from acceleration sensors.  

Cases:

• Balancing benefits and drawbacks
• Balanced Scan stage for in Electron microscope
• Fully flexure-based large range of motion precision hexapod
• Increasing load capacity and support stiffness of flexures by overconstraining
• Using permanent magnets to reduce actuator force