A linkage-based character designed with Linkage and simulated in Algodoo.


A Strandbeest on a beach.

Theo Janson's strandbeests made from yellow plastic tube (Dutch electricity pipe) are able to walk and get their energy from the wind [1].

A man walking beside the strandbeest on a beach.

This work utilises human knowledge of mechanics and dynamics of linkage systems to create morphological structures, and it inspired me greatly.

The Process of Making

Stage 1 - Study

Wolf is a symbol of guardianship, ritual, loyalty, and spirit. I love the character of wolf and I'd like to build a robotic wolf myself as a pet since I was very young. it says the personality traits of the wolf are those of powerful instinct, intuition, and high intelligence, living in a community.

My exploration starts with a thorough research on the anatomy of wolves to understand their body structure and movement patterns.

sketches of wolves

Image source:

Sketches of wolf movements

I also made some initial sketches to trace wolves' leg movement patterns on my sketchbook. This would allow me to better understand and define the desired coupler curve space in later stages.

Analysis shows that, the walking mechanism of a wolf is appropriate challenging but intuitive to understand.

Given the time constraint and my skill levels, I traced the primary linkage mechanism based on the movement of a wolf's four legs, the head, and the tail, ignoring other complex structures.

Stage 2 - Design

Mobility - calculated by CKG (Chebychev-Kutzback-Grubler) criterion.

The project requires only one single actuator to drive the mechanism (i.e. M=1)

Basic Linkage - 4-bar linkage

M = 4 - 3(4-4+1) = 1

In this project, each leg is modelled by 6-bar linkages (Klann) with multiple 4-bar linkages. Two actuators were first implement to simulate the motion and this would be replaced by gears & belts afterwards.

With trial and error, this mechanism can achieve a relatively more stable results than the running mechanism shown earlier.

The final decision was made afterwards - a walking robotic wolf linkage character, based on a Disney's cyber tiger project [2]. After the linkage stucture was determined, I designed the models in Algodoo, and get inspired from a Gallop project by Mori-j [3].

Technical difficult -> Reasons for unstable structure - why would things blow up in Algodoo?

  • weight of objects

  • collision on 2D space

  • gravity and air-resistance

To overcome the limitation of Algodoo simulation, a procedure was developed in terms of material set-up and a sanity check on collision.

I used parallel linkage mechanism for in-phase rotation, using two circles with internal gears of collision plus friction for a change of rotational direction.

The final look of the linkage structure in completion.

I used springs to create more realistic feeling of walking. The spring constant is set to a small value due to negligible mass of objects, but the damping factor is set to a large value in order to achieve critical or even over-damped 'oscillation' of the system.

Adding the 'skin' to my robo-wolf.

With a monotone colour code to the desired artisitc effect.

Learning & Reflection

This project enabled me to use creative engineering tools to accompolish tasks that involve linkage structures. During the process, I learnt to solve problem by using Community Forum effectively and look for documents and learn from trial-and-error independently.

I learnt that a systemic debug process is important, and a standard operation procedure will save me much time.

The best way to keep learning in mind is to document everything clearly (and with a narrative) in a logbook. A ditigal lookbook that allows me to insert pictures (like OneNote) was of great help during the execution of the project.

Useful references: