Adjustable Stiffness Spring


September 2014 – March 2015


Nowadays, there are a variety of adjustable stiffness springs (springs which can change its stiffness) on the markets, which are applied in various fields of engineering. However, most of them are big and expensive, and the range of the adjustment is not broad enough. Also, the stiffness of the spring cannot change continuously and instantly. These disadvantages make it unable for the ordinary consumers to purchase and apply the stiffness spring to the various areas of life.

Therefore, we designed a new type of adjustable stiffness spring. It consists of two springs which have the different stiffness and the two springs can rotate separately. Its volume is relatively small, and we can use PS2 to control the step motor wirelessly, thus we are able to control the stiffness of the spring wirelessly.

Our main tasks developed to solve the problem are designing and manufacturing. Since we need to make the spring small and work efficiently at the same time, it took us lots of effort to design a proper one. Also, in order to improve the accuracy the parts, we choose to use 3D print technology and it increases the difficulty of manufacturing.

After we completed manufacturing the prototype, we tried to test the highest and lowest stiffness, and draw the force versus displacement diagram for both springs. The diagram shows that our spring has a broad range of adjustment compared with the previous springs and we can change the stiffness continuously.

In conclusion, our adjustable stiffness spring meets most of the design requirements. The spring has a relatively broad range of adjustment, and we can change the stiffness of spring continuously and wirelessly.

In the future, our spring can be applied into many fields, like the suspension system of the bicycle and the car, the joints of the robots. When we make the volume of spring small enough, we can even apply the spring to the shoes to make them more comfortable.

Design Structure

Demo video



Click here to see detailed project document.