Design of Stabilizing Arm Mechanisms for Carrying and Positioning Loads

Stabilizing arm mechanisms are used to support and position a load with minimal force from the user. Further, stabilizing arm mechanisms enable operators to stabilize the motion of the load while walking or running over variable terrain. Although existing stabilizing arm mechanisms have reached fairly broad adoption over a range of applications, it remains unknown exactly how the spring properties and geometric parameters of the mechanism enable its overall performance. We developed a simplified model to analyze the vertical dynamics of stabilizing arms to determine how the spring properties and mechanism geometry affect the natural frequency of the load mass, the range of load masses that can be supported, and the equilibrium position of the load mass. We found that decreasing the unstretched spring free length is the most effective way to minimize the natural frequency; the spring lever arm can be used to adjust for a desired load mass range, and the linkage length can be used to adjust the range of motion of the stabilizing arm. The spring stiffness should be selected based on the other parameters. This work provides a systematic design study of how the parameters of a stabilizing arm mechanism affect its behavior and fundamental design principles that could be used to improve existing mechanisms, and enable the design of new mechanisms.