Development of a mechanically coupled, six degree-of-freedom load platform for biomechanics and sports medicine

Six degree-of-freedom force sensors measure the three forces and three moments applied to a body. In general, there are two main design methodologies for six degree-of-freedom force sensors: mechanically decoupled and mechanically coupled designs. Mechanically decoupled force sensors have the advantage of low cross-sensitivity between the different axes. Unfortunately, decoupled designs necessitate a complicated geometry that leads to difficulties in manufacturing. In a mechanically coupled force sensor, the output signals cannot be attributed directly to specific force/moment components. Instead, the applied loads are derived by multiplying the output signals by a decoupling matrix. This additional computational effort is offset by the simplicity of the design. This paper describes the development of a mechanically coupled, six degree-of-freedom load sensor that combines high accuracy and ease of manufacture. The sensor geometry was optimized and the decoupling matrix determined through finite element analysis. A prototype sensor was manufactured and tested. The experimental results validated the analysis and demonstrated the potential advantages of such a sensor.