**Nomenclature**


*Enhanced Nonlinear PID Controller for Positioning Control of Maglev System DOI: http://dx.doi.org/10.5772/intechopen.96769*

*xr* reference input *Emax* maximal error *Erms* root mean square error

**Acknowledgements**

support.

**Nomenclature**

*M* steel ball mass *Nw* number of windings *xo* nominal displacement *io* nominal current

*Ka* power amplifier *Ks* sensor sensitivity

*i* current *x* displacement

*K* electromagnetic constant

*g* gravitational acceleration *Fm* electromagnetic force *Fg* gravitational force

*g* gravitational acceleration *Kc* current coefficient *Kx* position coefficient *β* open loop gain *γ* open loop pole *α* third pole location *ζ* desired damping ratio *ω<sup>n</sup>* desired natural frequency

*Kp* proportional gain *Ki* integral gain *Kd* derivative gain

*Gp* plant model

*GPI-PD* PI-PD control

*T* sampling time

*e* tracking error

**108**

*Kpb* feedback proportional gain *Kff* linearized feedforward gain

*δdesired* desired characteristic equation

*Gz* disturbance compensator

*ω<sup>c</sup>* system cutoff frequency **K** state feedback gain matrix *ufb* feedback control signal *uff* feedforward control signal *u* summation signals of *ufb* and *uff*

*N* number of data sample

*Gff* model-based feedforward control

*Kz* linearized disturbance compensation gain *δPID* closed loop PID control characteristic equation *δPI-PD* closed loop PI-PD control characteristic equation

*Td* time constant of derivative elements with filter

The authors would like to be obliged to Motion Control Research Laboratory, Center for Robotics and Automations, Faculty of Electrical Engineering, Universiti Teknikal Malaysia Melaka for providing the laboratory facilities and equipment

*Control Based on PID Framework - The Mutual Promotion of Control and Identification…*
