Bioinspired Control Architectures for Multilegged Locomotion

The primary aim of this research is to discover control principles for multi-legged locomotor systems that will allow them to move safely over soft surfaces. The secondary aim is to understand what determines the amount of energy it takes to move on these soft surfaces. The results of these aims will be synthesized to propose a control architecture that is both stable and energy efficient for multi-legged systems moving on soft surfaces. This research has broad, important applications in engineering and biology. Any robot designed to operate in the real world will innevitably encounter some form of compliant surface, upon which it must remain stable, and, if controlled properly, could reduce its energy consumption. This research would enable that robot to move safely and efficiently on soft surfaces. More agile, efficient robots have immediate and critical application to search and rescue, space exploration, and disaster relief. Furthermore, a better understanding of legged systems would enable us to build prosthetic limbs that work naturally on rough or moving terrain, and to provide better rehabilitation to those with neurological disease or injury. For biology, while we know that multilegged animals (>2 legs: the overwhelming majority of them) routinely handle compliant surfaces, we don't know how these surfaces affect their stability or energetic consumption. This means we don't understand how the environment has shaped them throughout evolutionary history. Further, their mechanisms of dexterity on compliant surfaces remain an untapped source of bioinspiration. Thus the basic scientific results of this proposal have fundamental import in robotics, medicine, and biology.To reach these aims we require three things: 1) a way to specify and systematically vary the controller in a running multi-legged system; 2) a way to measure its stability and energy consumption; and 3) a way to search through the large space of possible controllers in a reasonable amount of time. This proposal will meet these challenges with a cross-displinary approach that integrates results from robotic and animal studies. The robot provides a platform in which the controller can be directly specified and systematically changed, while the stability and energetic consumption of it's motion can be readily measured (the on-board power management circuitry gives energy consumption directly). Because there are a huge number of ways to organize the control of multiple legs, we will use measurements of how trotting dogs adjust for compliant surfaces to guide how we vary the controller in the robot. Measurements of how dogs adjust for the compliant surface will be taken back to the robot, programmed into it's controller, and the effects of making those changes quantified in a real, moving system. This overcomes the problem with animal experiments that it is not known what control architecture the animals is actually using, as well as the limitation of using computer simulations to design controllers, which is that current models of foot contact are often so unrealistic that they can't be used to predict the behaviour of a real world robot or animal.We choose dogs because they are known to be agile, efficient runners, even in the face of a dynamic environment, and past research has shown that both dogs and the legged robot RHex have similar bouncing gaits. They can be safely challenged with a soft surface, and yet are large enough to measure the stability of their body and the motion of their individual limbs. Past insect and mathematical research has suggested that by acting as a point mass with an elastic spring leg actuated at the hip (the clock-torqued spring loaded inverted pendulum, or CT-SLIP), a multilegged system may be able to handle soft surfaces with simple, feedforward control. The robot will be programmed with this controller as a starting point, and the animal (a trotting dog) is known to behave in this manner on rigid surfaces.

The aim of this project is to improve our control architectures for multi-legged locomotion, by comparing perturbation experiments on a cutting edge legged robot with an extraordinarily capable natural runner, the trotting dog. These improvements in control will enable us to build more agile and economical robots. Because the UK currently lags behind the US and Japan in robotics research and commercialization, this proposal represents an important strategic investment in UK robotics. Without an improved understanding of legged locomotor control, we cannot build prosthetic devices that enable amputees to walk naturally on rough terrain, we are limited in our ability to rehabilitate those with neurological disorders, and we miss opportunities to improve animal welfare and to build agile robots that assist us in search and rescue, disaster relief, and mine clearance. The accessible yet multifaceted nature of the project make it an ideal vehicle for public engagement with science, and a valuable asset to third sector organizations such as the Science Museum. In sum, the basic scientific importance, commercial applications, and publicly accessible nature of this project give it broad impact across the academic, commercial, and public sectors. This proposal represents a timely and strategic investment in the UK's commercial sector that will bolster its economic competitiveness. The International Federation of Robotics and the United Nations Economic Commission Europe recently predicted that the robotics industry will be worth 38 billion by 2025. This proposal will engage with UK based active prosthetic device makers Chas A Blatchford, surgical robotics company Acrobot, and dextrous robot manufacturers Shadow Robot. The project is especially well matched to active prosthetic limb design, as its improvements in control architecture could make these limbs more stable and energy efficient when used to move on soft or dynamic environments. Opportunities for commercialization in prosthetics, surgical, service, and entertainment robotics will be sought with these UK robotics companies and others, through the experienced commercial applications team at the Royal Veterinary College. In the public sector, points of impact will be undertaken in medicine, animal welfare, defense, hazardous waste cleanup, and search and rescue operations. The PI's group provides biomechanics support for two of the leading orthopaedic hospitals in the UK, the Royal National Orthopaedic Hospital and the Nuffield Orthopaedic Centre. The potential for results from this project to aid in clinical gait rehabilitation will be discussed with investigators at each of these hospitals. Further, the Farm Animal Welfare Council stated in 1997 that lameness is the most important animal welfare problem in the dairy industry , with one in two dairy cattle affected by lameness each year. This proposal will shed light on which surfaces are optimal for preventing animal lameness, and will be pursued through the group's contacts built up during a recently completed, three year DEFRA project on cow lameness. The wider public will be engaged through a scientific outreach and education event, media activity, and a dedicated website, capitalising on the exciting, accessible natures of animal locomotion and robotics. An open day will be held at the Structure and Motion Laboratory, entitled Dogs and robots on springs: how many-legged animals move , including demonstrations of the robot and technologies used at the frontier of motion science. Media coverage will be exploited to publicize the project with the aid of the RVC's PR consultants. The PI has experience with and enthusiasm for engaging with the media, having recently appeared in The New York Times, Time.com, New Scientist, the Daily Telegraph, National Public Radio (US) and the TV network ESPN (US).