E. Dragoni, I. Spinella, A. Spaggiari, Università degli Studi di Modena e Reggio Emilia, Reggio Emilia, Italy
Shape memory alloys (SMAs) are smart materials exploited in many applications to build actuators with high power to mass ratio. Depending on the shape of the active material, these actuators have also several drawbacks: SMA wires show poor stroke and excessive length, helical springs have limited bandwidth and high power consumption.
This work is focused on the design of a linear SMA actuator conceived to maximize the stroke while limiting the overall size and the electric consumption. This result is achieved by adopting for the actuator a telescopic multi-stage architecture and using SMA helical springs with hollow cross-section.
The design process complies with a Quality Function Deployment approach. The design starts with the House of Quality, which is built around the customer needs identified for the field of linear SMA mini-actuators. Output of the House of Quality is a set of technical specifications that the actuator must satisfy in order to overcome existing competitors in the SMAs actuator field.
Following the House of Quality, a structured conceptual design procedure is presented, leading to a portfolio of concepts. These ideas are evaluated using the decision-matrix method to satisfy the customer needs. The best concept is a linear actuator based on a telescopic design: several concentric modules are assembled to achieve the desired stroke, with each module powered by a set of hollow SMA helical springs. As described in a previous work of the authors, the hollow geometry leads to reduced axial size and mass of the actuator and to enhanced bandwidth,.
An analytical thermo-electro-mechanical model is developed to optimize the device. Output stroke and force are maximized while total size and power consumption are simultaneously minimized. Finally, the optimized actuator, showing excellent performance from all these points of view, is designed in detail.
Summary: Shape memory alloys (SMAs) are smart materials exploited in many applications to build actuators with high power to mass ratio. Depending on the shape of the active material, these actuators have also several drawbacks: SMA wires show poor stroke and excessive length, helical springs have limited bandwidth and high power consumption.
This work is focused on the design of a linear SMA actuator conceived to maximize the stroke while limiting the overall size and the electric consumption. This result is achieved by adopting for the actuator a telescopic multi-stage architecture and using SMA helical springs with hollow cross-section.
The design process complies with a Quality Function Deployment approach. The design starts with the House of Quality, which is built around the customer needs identified for the field of linear SMA mini-actuators. Output of the House of Quality is a set of technical specifications that the actuator must satisfy in order to overcome existing competitors in the SMAs actuator field.
Following the House of Quality, a structured conceptual design procedure is presented, leading to a portfolio of concepts. These ideas are evaluated using the decision-matrix method to satisfy the customer needs. The best concept is a linear actuator based on a telescopic design: several concentric modules are assembled to achieve the desired stroke, with each module powered by a set of hollow SMA helical springs. As described in a previous work of the authors, the hollow geometry leads to reduced axial size and mass of the actuator and to enhanced bandwidth,.
An analytical thermo-electro-mechanical model is developed to optimize the device. Output stroke and force are maximized while total size and power consumption are simultaneously minimized. Finally, the optimized actuator, showing excellent performance from all these points of view, is designed in detail.
