Development of a highly efficient bridge-type mechanism based on negative stiffness

The bridge-type mechanism is one of the most widely used displacement amplifiers in micro-scale applications. However, a bridge-type mechanism with an external load always works in an energy-inefficient situation due to the storage of strain energy in the flexural hinges, which can be validated by the analytical model established in this paper. In fact, in the majority of cases, the energy efficiency of this type of mechanism is only about 50%. To solve this problem, a highly efficient bridge-type mechanism based on negative stiffness is proposed in this paper, which features compact size, simple design, symmetric structure, and also high efficiency. The potential energy in the negative stiffness mechanism acts as an additional energy stream to maintain the total potential energy constant in the system, i.e. the input energy from the actuator can be totally transformed into the output energy, therefore the energy efficiency is close to 100% in an ideal situation. To validate the feasibility of the proposed solution, a prototype of the highly efficient bridge-type mechanism is fabricated. The experimental results show that the efficiency has been improved to 90% approximately when the negative stiffness mechanism is employed. The proposed design can be employed and extended to other compliant mechanisms where high efficiency is required.