MIRA University of Twente
Department of Biomechanical Engineering

Department of Biomechanical Engineering

Balroom - Time variant ankle stiffness


Twente University (also open for students from TU Delft)


(Bio-)Mechanical engineering




Denise Engelhart (Twente, daily supervisor)

Alfred Schouten



Postural instability and falls are common and devastating features of ageing and many neurological, visual, vestibular or orthopedic disorders. To unravel the underlying pathophysiological mechanisms closed loop system identification techniques (CLSIT) are used. The advantage of CLSIT is that it ‘opens the loop’ of a system in which the controlled variable (body sway) is fed back to the control variable (torque due to muscle activations). The underlying (patho) physiological mechanisms of balance control can be identified, leading to standardized and unbiased results.


The mechanical behavior of a joint can be described by a (linear) musculoskeletal model of a human limb with intrinsic feedback due to the visco-elasticity of active muscles, and with reflexive feedback (length, velocity and force) of muscle afferents (muscle spindles and Golgi tendon organs). Nevertheless, the visco-elastic properties of for instance the ankle joint depend on the position of the joint and therefore vary during movement. We want to investigate this non-linear behavior using Time Varying CLSIT and see how the physiological parameters change over time.


The Bilateral Ankle Perturbator (BAP) consists of two small foot-size platforms driven by an electromotor, which can rotate around the ankle axis; therefore different angles of the ankle can set and reaction measured over time. The aim is to develop novel techniques to identify TV ankle stiffness using the BAP.


o Literature review on mechanical behavior of a joint including different feedback loops and important physiological parameters.

o Develop new techniques for time (parameter) varying system identification.

o Study the effect of non-linear movement of the human body (slow adaptation) on parameter estimation with the new TV CLSIT

o Study the effect of non-linear perturbation amplitude (sudden adaptation) on parameter estimation with the new TV CLSIT

o Write a report in the form of a scientific paper

Further information

If you are interested in this assignment, please contact Alfred Schouten (a.c.schouten@tudelft.nl) or Denise Engelhart (d.engelhart@utwente.nl) for further information.