UC Berkeley

Back injuries are the most common musculoskeletal disorder in the workplace and cost employers billions of dollars each year. Although these are widely known statistics, no comprehensive solution exists to reduce back injuries. While products like dollies and carts have been designed to solve particular tasks like moving materials, an all-encompassing solution to alleviate back injuries has yet to be proposed. This is largely due to the dynamic complexity involved with accommodating the various tasks required by different occupations. While the majority of some workers spend their days stooping to move materials, others predominantly walk bent over to perform duties like vacuuming.

But at the most basic level, professions with high rates of back injuries mainly have two common motions: stooping and walking. Therefore, to successfully reduce back injuries, a device must reduce back muscle strain by supporting the torso during stooping while still permitting walking. This dissertation proposes five hip actuation designs to solve this fundamental problem. The intent is for the hip actuators to be incorporated into a full exoskeleton which interfaces with the user’s torso and legs to support the lower back during stooping and/or walking.

The first hip actuation design is a simple wrap spring clutch which is beneficial for tasks like static stooping and bent walking (walking while stooped). The second hip actuation design adds a spring to the first design to conserve energy and dynamically support the back during stooping and standing upright. The third hip actuation design adds a locking feature to the spring in the second design to control when the spring’s energy is released. The fourth hip actuation design uses one large, high-torque motor to support the torso during bending and walking. The fifth hip actuation design adds a wrap spring clutch to the fourth design to reduce the complexity of the control system when a user walks.

Although the proposed designs are discussed in order of increasing design complexity, the enhanced systems also accommodate additional worker tasks, making them applicable to broader audiences. Ultimately, a cost-benefit analysis weighing design complexity versus applicable tasks is necessary to determine which designs are most beneficial for production.