Alexander (Sandy) Enoch PhD

Sandy Enoch

Research Interests

My research centres around bipedal locomotion and involves creating a novel biomorphic robotic platform which is capable of multimodal locomotion. I am especially interested in variable stiffness actuators and the optimal control of such joints. For my PhD I will be creating a biomorphic bipedal robot that mimics the human ability both to vary the stiffness of joints and store energy in compliant linkages. I will investigate neurologically inspired control methods based around reflexive modulation of rhythmical control signals using data gleaned from experiments and simulations. In parallel with this I will be looking at the representation and generation of optimal periodic movements with regard to energy expenditure, stability etc.
Traditionally bipedal robots have fallen into one of two categories: joint control, whereby rigid joints follow an exact pre-planned trajectory; and passive-dynamic, where minimal actuation is provided to a system mechanically tuned to oscillate and provide a naturally efficient walking behaviour. Whilst joint control robots are extremely versatile, and can perform any number of tasks, they are also very inefficient in their movements and generally vulnerable to external disturbances. Conversely, passive-dynamic walkers can produce very efficient locomotion at a single set speed, with some robustness to disturbances, but can perform no other tasks. By creating a robot capable of varying the effective joint stiffness it is aimed to create a platform which combines the advantages of both joint-control and passive dynamic approaches.
It is incredibly difficult to measure how the instantaneous stiffness of human joints changes as we walk. The creation of an anthropomorphic bipedal robot which can vary its joint stiffness explicitly will allow us to elicit more information about possible joint stiffness profiles in humans.
Prior to beginning my PhD project I completed the DTC neuroinformatics MSc with a masters thesis entitled "Age related effects on strategy switching ability in a virtual plus maze". Before this I gained an MEng in robotics from Heriot-Watt university.

  Rapid Manufacture of Novel Variable Impedance Robots using Waterjet Cutting and 3D Printing
Enoch, AM & Vijayakumar, S 2015, 'Rapid Manufacture of Novel Variable Impedance Robots using Waterjet Cutting and 3D Printing' Journal of Mechanisms and Robotics, vol 8, no. 1, 011003. DOI: 10.1115/1.4030388
Variable stiffness and variable damping can play an important role in robot movement, particularly in legged robots such as bipedal walkers. Variable impedance also introduces new control problems, since there are more degrees of freedom to control, and the resulting robot has more complex dynamics. Among other applications, we are investigating the effects of impedance variation and physical compliance on bipedal locomotion. In order to do this it we have developed novel bipedal robots which can vary both the stiffness and damping of their joints, independently of the joint's output position. As a lab which primarily develops algorithms, we only have access to very limited manufacturing facilities, and must factor this in when developing hardware to be built. Rapid manufacturing technology allows for cost effective outsourcing of parts, but each process has its limitations. We present our experiences in producing bipedal robots with variable impedance joints using waterjet cutting, 3D printing, and posit that combining these two techniques provides a simple, fast, and cost effective way to produce robotic hardware.
General Information
Organisations: Institute of Perception, Action and Behaviour .
Authors: Enoch, Alexander M & Vijayakumar, Sethu.
Number of pages: 11
Publication Date: Aug 2015
Publication Information
Category: Article
Journal: Journal of Mechanisms and Robotics
Volume: 8
Issue number: 1
ISSN: 1942-4302
Original Language: English
  BLUE: A bipedal robot with variable stiffness and damping
Enoch, A, Vijayakumar, S, Sutas, A & Nakaoka, S 2012, BLUE: A bipedal robot with variable stiffness and damping. in 2012 12th IEEE-RAS International Conference on Humanoid Robots (Humanoids 2012). IEEE, pp. 487-494, 2012 12th IEEE-RAS International Conference, Osaka, Japan, 29/11/12. DOI: 10.1109/HUMANOIDS.2012.6651564
Exploiting variable impedance for dynamic tasks such as walking is both challenging and topical - research progress in this area impacts not only autonomous, bipedal mobility but also prosthetics and exoskeletons. In this work, we present the design, construction and preliminary testing of a planar bipedal robot with joints capable of physically varying both their stiffness and damping independently - the first of its kind. A wide variety of candidate variable stiffness and damping actuator designs are investigated. Informed by human biophysics and locomotion studies, we design an appropriate (heterogenous) impedance modulation mechanism that fits the necessary torque and stiffness range and rate requirements at each joint while ensuring the right form factor. In addition to hip, knee and ankle, the constructed robot is also equipped with a three part compliant foot modelled on human morphology. We describe in detail the hardware construction and the communication and control interfaces. We also present a full physics based dynamic simulation which matches the hardware closely. Finally, we test impedance modulation response characteristics and a basic walking gait realised through a simple movement controller, both in simulation and on the real hardware.
General Information
Organisations: Institute of Perception, Action and Behaviour .
Authors: Enoch, Alexander, Vijayakumar, Sethu, Sutas, Andrius & Nakaoka, Shinichiro.
Number of pages: 8
Pages: 487-494
Publication Date: 2012
Publication Information
Category: Conference contribution
Original Language: English

Research press coverage:
Sandy Enoch discusses study suggesting nearly a third of UK job could be at risk of being taken over by robots

Efficient Adaptive Bipedal Locomotion through Variable Stiffness and Damping (PhD)