Low Power Valve Actuation Using Trans-Permanent Magnetics

Abstract

The subject of magnetic actuators is very broad, and encompasses a wide range of technologies, magnetic circuit topologies, and performance characteristics for an ever-increasing spectrum of applications. As a consequence of recent advances in soft and hard magnetic materials and developments in power electronics, microprocessors and digital control strategies, and the continuing demand for higher performance motion control systems, there appears to be more research and development activity in magnetic actuators for applications spanning all market sectors than at any time. Thus many actuator types and topologies are emerging with widely varying operational characteristics, in terms of displacement (rotary or linear), speed of response, position accuracy and duty cycle.

In this dissertation, a rational approach for switching the states of permanent magnets through an on-board magnetization process is presented. The resulting dynamic systems are referred to as trans-permanent magnetic systems (T-PM). The first part of this research focuses on the governing equations needed for the analysis of trans-permanent magnetic systems. Their feasibility is demonstrated experimentally. In doing so, a method that has the potential of leading to new ultra-low power designs for electromechanical devices is introduced.

In the second part of this research, the aforementioned developments in T-PM are applied to the problem of low power valves. Whereas alternate approaches to low power valve control may utilize latching to maintain valve position during inactive periods, an approach that eliminates the need for latching mechanisms is presented. Instead, the principles of T-PM are employed to switch the states of permanent magnets; the used of permanent magnets instead of electromagnets eliminates power consumption during inactive periods, thereby reducing power consumption to ultra-low levels.

The magnets in a T-PM actuator are configured in a stack. The relationships between the strength and number of magnets in the stack and the stroke and resolution of the actuator are developed. This dissertation reports on the design and testing of a prototype valve actuator that uses a stack pf T-PM with alternating polarity. It is shown that this stack is well suited for discrete state process valves having a small number of states. It is concluded that the trans-permanent valve represents a promising valve actuation technology.