Spool position feedback in an electrohydraulic valve typically requires a spool displacement sensing device such as a LVDT. Self-sensing is the methodology to obtain spool displacement information directly from the solenoid spool actuators, thus obviating the additional cost and footprint of a LVDT or another displacement sensing device. A self-sensing scheme that uses only the measurement of e...

This paper proposes a variation on a sliding mode control approach that provides significant energy savings for the control of pneumatic servo systems. The control methodology is formulated by first decoupling the standard four-way spool valve used for pneumatic servo control into two three-way valves, then using the resulting two control degrees of freedom to simultaneously satisfy both the sl...

In this paper, we present a cable mechanism which synthesizes a nonlinear rotational spring from a linear spring. The nonlinearity is realized by winding the cable around a spool which has a varying radius. We show that for a given nonlinear torque profile (synthesis objective) there is an explicit geometric expression of the shape of the spool which synthesizes this profile. We present the geo...

To investigate the aerodynamic characteristics of fan in windmilling conditions, a new body force model with rotational speed prediction was developed. The built based on balance output torque and resistance torque. spool can be iteratively solved simultaneously solving governing equations without requiring mass flow rate or other inputs. comparison experimental results shows that using accurat...

Electro-hydraulic proportional control valves are widely applied for motion control in the electro-hydraulic fluid power system. Normally, a sliding spool is used in the proportional control valve to control the flow direction and flow rate passing through the valve, as a result, the meterin and meter-out orifices are mechanically connected [1]. The sliding spool makes the system robust and eas...

Stack-type piezoelectric actuators, which usually consist of several ceramic layers connected in series, are widely used in piezoelectric direct-drive servo valves (PDDSV). However, poor pulling force capacity of this kind of actuators affects the performances of the direct-drive servo valves. This article presents a new type of PDDSV, whose spool-driving mechanism is composed of a set of indep...

In this article, an exact analysis of compressors spool in a turbojet engine has been investigated. The spool is modeled as a rotating thick-walled hollow circular cylinder with free-clamp ends. It is subjected to centrifugal load due to its constant rotational speed, uniform internal and external radial loads and arbitrary thermal gradients. The analysis is initially investigated for the homog...

In this paper we present a cable mechanism that realizes a nonlinear rotational spring from a linear translational spring. The spring is pulled by a cable wound around a non-circular spool, which is rigidly attached to the joint. The non-circular shape of the spool induces a nonlinear relationship between its angular position and the torque created by the tension of the cable. Depending on the ...