Reduction of Self Induced Vibration in Rotary Stirling Cycle Coolers
Cryocooler is a major consideration in the design of IR imaging systems, especially when mounted on stabilized platforms with gimbals. The coolers in these types of applications induce forces and moments that interfere with proper stabilization of the camera leading to image blurring and loss of pointing accuracy. This phenomenon is known as “jitter” and presents a challenge to the motion control system engineer. To overcome this problem system designers often elect to avoid the use of rotary Stirling machines and instead select linear split Stirling or pulse tube coolers. Thus, they trade off size, input power, and reliability for image quality. This paper deals with the problem of a rotary cooler's self-induced vibration and ways to eliminate or minimize its affect on imaging system performance. In this paper we will point out the vibration sources in rotary coolers and methods to reduce their magnitude. Also, we will present actual test data of a cooler with dynamically balanced crack mechanism and an external torque vibration absorber, and compare it to a standard cooler.