Kinematic Design and Applications of Flexures
This chapter first discusses, in a systematic way, various ways to constrain the degrees of freedom (DOFs) of a simple rigid body, starting by constraining one DOF and adding additional constraints until the body cannot move. Typical structural elements called struts and various forms of leaf springs are introduced. Each of these is capable of restraining one or more DOFs. Collectively, these elements are commonly known as flexures. The invaluable benefit of thinking in terms of controlling DOFs is that it allows the user to lay out support structures (and mechanisms) without having to do any calculations. Just by reasoning, support structures can be defined. Having done that, the structural elements are dimensioned by taking into account the body loads, the performance requirements, and environmental inputs. A satisfactory solution is not always found the first time. Iterations may be necessary. With experience, the user will quickly arrive at the best solution, i.e., one using minimum material to achieve maximum performance. The hardware described or referenced in this chapter ranges from simple optomechanical subassemblies to high-level systems. Application of the rules given here for properly constraining each DOF applies at all levels of complexity. Many examples of simple flexure mountings are given here. Additional examples are included elsewhere in this book.