一种恒力机构的设计与测试

Design and test of a constant force generator

为配合基于牛顿第二定律的微重力环境下质量测量等恒力装置的需求,设计了一种基于弹簧–凸轮–转轮的恒力机构,弹簧–凸轮生成恒定力矩,恒力矩通过转轮输出恒定拉力。利用AutoCAD进行理论仿真,恒力理论精度达0.2%。设计了一种基于升降台和电子天平的拉力测试方法。基于此方法精确测定了弹簧的刚度系数,验证了弹簧调整机构的有效性,实现了小于0.5%的匹配误差。基于此方法对恒力值进行测定,从而以此为基础对恒力机构进行调整和修型,最终恒力机构在180mm行程范围内实现了1%的拉力恒定性,为后续基于牛顿第二定律的微重力质量测量方法的研究提供了可靠的平台。

Constant force generator is an essential part in applications such as measuring mass in micro-gravity environment using Newton’s Second Law. This paper presents a constant force generator consisting of a spring-cam structure and a wheel. Spring-cam structure generates a constant moment, and the wheel outputs a constant force. Simulated in the AutoCAD software, the generator gives a relative error of 0.2%. Force measurement method is also presented based on a electronic scale and a lifting device. By this method, spring stiffness is precisely measured, the spring adjustment structure is proved effective and stiffness is adjusted to give an error less than 0.5%. Constant force is also tested by this method, and after adjustment and refinement, the constant force gives an error about 1% within 180 mm range. The apparatus is proved to have high performance and can be used as basic platform for subsequent research on mass measurement method in micro-gravity environment.