Qinqi Xu on secondment

Host Institution: Vrije Universiteit Amsterdam, Netherlands.

Dates of Stay: November 14th to December 9th 2016.

Research topic:

  • Visuo-motor control
  • Project: How seeing articulated tools helps guide the tip of the tool to its target


  1. Objectives

The objective of the secondment is to facilitate sharing of knowledge and new skill acquisition in visual-motor control, enable networking activities for the secondee, and to promote collaboration and sharing of techniques between university and research institute. The work is carried out at VU Amsterdam, Netherlands, under the supervision of Prof. Eli Brenner. The aim of the research project is to investigate how visual representation and mechanism complexity influence reaching with a tool.


  1. Activities

My stay at VU Amsterdam aimed at evaluating the role of visual feedback in the control of articulated object, as part of my Ph.D. research ‘Control and representation of articulated objects’ at IIT, Italy. The activities conducted during this secondment consisted mainly in performing psychophysics experiments and modeling of the tool visuo-transformation.


a. Kinematics transformation modelling

A first task consisted in kinematics modelling of the tool, which aimed to provide an estimation on how complex the kinematics transformation would be in reaching the targets with the tool.


b. Joint types and complexity selection

The next step consisted in studying the transformation and target space of tools involving different types of joints and of variable level of complexity. The aim when selecting these tools was to cover a wide range of difficulty levels and transformation frames. Estimation was done with both kinematics and statistical modelling.


c. First psychophysics experiment

The tools selected to be used as stimuli in the first psychophysics experiment, included either revolute and prismatic joint or a combination of both. Three types of visual representations were provided: Pre-, continuous- and non-visual information. The movement trajectory and target number for each subject were collected to find out the effects of the visual representation and of the tool mechanism complexity on the reaching movements to the targets.


d.Second experiment comparing two types of tool configurations

To verify the effect of the number of links on visual feedback effect observed in the first experiment, a second experiment has been carried out including mechanisms with similar configurations transiting gradually from one type to another. A first specific objective was to examine whether there is a categorical distinction between two-link and four-link mechanisms. The second objective was to examine the distance hypothesis.


e.Third experiment with tools in similar configuration

The general goal of the third experiment was to confirm the observations of the first experiment and, in particular, the absence of visual affect with tool similar to the original parallelogram linkage. The tools involved in the third experiment to examine the visual effect were larger parallelograms, more similar in size with the tool used in the first experiment.


f. Other activities

Besides the experiments carried out during the stay, other activities were performed, for example, data analysis and journal club meetings.


    1. Main results:

a.Modelling of visuo-motor transformation of articulated tools.

b. Complement of three psychophysical experiments.

c. ECVP 2017 Poster Presentation.

d. A publication in preparation to be submitted to an academic journal.


  1. Conclusions

The stay in VU Amsterdam has offered me a great opportunity to work with scientists and experts in human movement research: it widens the perspective of my understanding in this field. The experiments in visual control in reaching movement with touch-screen trackpad is essential for the visuo-motor control study as part of my PhD project. The work contains both theoretical analysis and experimental verifications. The planned experiments were completed and the results turned out to be very interesting. It was a great challenge and a pleasant experience to me.

I would like to thank Prof. Eli Brenner and Prof. Gabriel Baud-Bovy for their guidance and contribution on this secondment project, and all the people of the Department of Human Movement Sciences at VU Amsterdam for their kind help and participation in my experiments.


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