Michael D. Sidman, Ph.D.

SIDMAN Engineering, INC.

Mechatronics  ▪  Motor & Motion Control  ▪  Servo Systems

magnetic disk drive

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This fully integrated, comprehensive simulation model and design tool allows rapid development and optimization of a complete disk drive head-positioning servo system.  Users can directly observe the performance and complex interaction of mechanical, electrical and digital control system dynamics.

The user can observe the internal states of each of the interconnected and simultaneously operating electrical, mechanical and control system (DSP) portions of the system. Based on MATLAB and SIMULINK, this flexible, open architecture tool allows designers to graphically explore a multitude of what-if possibilities, tune performance and debug problems prior to or concurrent with prototype development.


  • Dr. Sidman's simulation model integrates mechanical, electrical, digital servo and adaptive system dynamics.
  • Parameters are easily modified
  • Intuitive, instructive GUI block diagrams 
  • Simultaneously view mechanical, electrical and digital control system states with on-screen scopes
  • Model is customized and parameterized for your product application
  • Instruction on model usage

Simulation performs, track following as well as arbitrary length seeks in either direction, settling and track following operations utilizing a seek/settling profiles and deceleration anticipation.

  • Actuator dynamics include:
    • Bearing stiction
    • Arm/head/coil flexible modes (resonances)
    • Nonlinear bias torque
    • Power amplifier dynamics
    • Motor electrodynamics
    • A/D and D/A quantization.
  • Disturbances include: 
    • Repeatable and non-repeatable runout
    • Bias and cable forces
    • A selection of industry standard external shock and vibration sources
  • Modern digital state estimators and controllers
  • Control system design scripts are included


Purchasing a mature product like this that has been developed by an recognized expert both in disk drive digital servo systems and dynamics modeling saves the time, frustration and considerable expense of attempting to doing it yourself. However, you have the freedom to easily change both the simulation model structure and parameters as you see fit.

  • Optimization of the complete head positioning system including mechanics, electronics and digital control
  • What-if testing and optimization
  • Reduce risk and engineering expense by simulating and testing before committing to product development
  • Reduce time consuming and unnecessary mechanical changes
  • Reduce prototype testing time
  • Evaluate performance with worst case component tolerances
  • Compare competing control algorithms
  • Reduce seek time using advanced fast seek profile design tool
  • Improve both tracking accuracy and settling performance at high track densities and in presence of actuator friction
  • Explore operating shock and vibration robustness
  • Improve runout correction using high-performance runout adaptation


  • Disk Drive (HDD) Servo Systems Development
  • Servo/DSP Chip & Algorithm Evaluation
  • Controller and Mechanics Optimization
  • Velocity Profile and Settling Optimization
  • Adaptive Runout Correction
  • Compensator Evaluation & Optimization
  • Shock and Vibration Sensitivity Analysis


Below is an example of what a user would see on just two (of many) scopes displayed during a typical seek/settle simulation. Other simulation modes include: track follow, runout adaptation and correction, shock and vibration testing, bandwidth adaptation, actuator power amplifier response, and more.

 Simulation of a long seek on a 3.5" HDD with state-estimator based digital control.

A long seek with state-estimator based digital control (HDD)

Customized Simulation Models and Design Tools

Digital Servo Systems Short Course

MATLAB and SIMULINK Training is available

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MATLAB and SIMULINK are registered trademarks of The MathWorks, Inc.