Hexplorer is a six-legged walking robot developed at the University of Waterloo. The robot is controlled by a network of seven digital signal processors, six of which control three motors each, for a total of 18 motors. Brand new custom electronics were designed to house the digital signal processors and associated circuitry. A variable duty factor wave gait, developed by Yoneda et al. was simulated and implemented on the robot. Simulation required an in-depth kinematic analysis that was complicated by the mechanical design of parallel mechanism comprising the legs. These complications were handled in both simulation and implementation. However, due to mechanical issues Hexplorer walked for only one or two steps at a time.

The purpose of this study was to analyze kinetic and kinematic data of individuals with unilateral transtibial limb loss and the effect different alignments have on the individual’s gait while they walk over uneven terrain. Individuals with lower limb loss are currently having their prostheses dynamically aligned to ensure a satisfactory walking gait on level ground with smooth surfaces, usually in the clinician's office or hallway. This study was looking to determine whether or not current prosthesis alignment procedures are adequate for determining a satisfactory walking gait on non-level and non-smooth terrains as well level smooth surfaces. An effective and efficient walking pattern is necessary to prevent degenerative conditions within the bones, muscles or other tissues of the body, due to compensations of the gait pattern. Sometimes, individuals are able to mask any compensations if their safety is unaffected by their surroundings and they are able to maintain a gait that appears normal or optimal. However, if terrains used on a daily basis present a sense of insecurity, gait compensations could be more problematic to the individual and they need to be addressed and corrected as best they can. This study determined that while there were some changes in gait on the uneven surface, due to the number of subjects it is unclear whether the changes are significant. The individuals showed a decrease in walking speed and step length and an increase in step width. There were also changes in the peak axial force.

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Hexplorer is a six-legged walking robot developed at the University of Waterloo. The robot is controlled by a network of seven digital signal processors, six of which control three motors each, for a total of 18 motors. Brand new custom electronics were designed to house the digital signal processors and associated circuitry. A variable duty factor wave gait, developed by Yoneda et al. was simulated and implemented on the robot. Simulation required an in-depth kinematic analysis that was complicated by the mechanical design of parallel mechanism comprising the legs. These complications were handled in both simulation and implementation. However, due to mechanical issues Hexplorer walked for only one or two steps at a time.

A great deal of research has been done on the adaptive strategies of individuals who have been affected by a gait altering ailment, but there is little research on the adaptive strategies to imposed restrictions in the healthy population. The role of the ankle in healthy gait is to generate a “push-off” force to create forward propulsion of the body (Winter, 2004). The purpose of this thesis was to identify adaptation patterns and compensation strategies in individuals while wearing and not wearing a device to reduce ankle motion(Ankle Motion Minimizer – AMM). Motion capture and force plate data were collected to determine the lower body kinematics and joint powers during both level ground walking and obstacle avoidance tasks. Repeated Measure ANOVAs with an alpha level of 0.05 determined that differences in the ankle angles and the ankle, knee, and hip powers existed between the various conditions. Results showed that participants had a decreased range of motion and power production at the ankle joint while wearing the AMM. Meanwhile, an increase in the power bursts from the ipsilateral knee were observed during the AMM conditions as well as small increases at the contralateral ankle and ipsilateral hip during the unilateral AMM condition. EMG analysis showed a distinct muscle activation pattern for each individual muscle during the different conditions. From this investigation, individuals who are unable to produce power through the ankle joint, were able to increase power propulsion predominately at the knee to compensate for the lack of propulsion provided by the ankle, therefore allowing ambulation to continue.

Bipedal locomotion is a challenging control engineering problem due to the non-linear dynamics and postural instability of the bipedal form. In addition to these challenges, some dynamical effects such as the ground reaction force are difficult to model accurately in simulation. To this end, it is essential to develop physical hardware to validate walking control strategies and gait generation methods. This thesis develops an on-line walking control strategy for humanoid robots and the electromechanical design of a physical platform for experimental validation. The first part of the thesis presents the development of a 14 degrees-of-freedom (DOF) lower body humanoid robot. The initial electromechanical design of the proposed system is derived from dynamic modeling of a general multibody system. Kinematic trajectories for the lower body joints are extracted from motion captured human gait data to form the preliminary design specifications. The drivetrain components are selected by analyzing the mechanical power requirements, torque-speed profiles, efficiency and thermal characteristics of actuators. The supporting mechanical chassis and power transmission system are designed to raise the center-of-mass (to reduce the swinging inertia of each leg) while minimizing the overall weight of the system. Refining the design of a complex multibody robotic system like the biped is an iterative process. The mechanical model of the system is transferred from Computer-Aided-Design (CAD) software to a dynamic simulator for analysis and the design is revised to improve performance. This iterative approach is necessary as small changes in the mechanical model can have significant impact on the overall dynamics of the system as well as implications for control design. A streamlined prototyping toolchain is developed in this thesis to extract the relevant kinematic/dynamic parameters of a mechanical system in CAD and automatically generate the equivalent system in a dynamic simulator. This toolchain is used to revise the electromechanical design and generate forward dynamics simulations. The second portion of this thesis develops a novel walking control strategy for on-line gait synthesis for 3D bipedal robots based on Wight's Foot Placement Estimator (FPE) algorithm. This algorithm is used to determine the desired swing foot position on the ground to \emph{restore} balance for a 2D bipedal robot. The FPE algorithm is extended to the general 3D case by selecting a suitable plane in the desired direction of motion. Complete gait cycles are formed by combining a finite state machine with the 2D FPE solution along the selected plane. Gait initiation is accomplished by computing state-dependent task space trajectories on-line to produce a forward momentum along the selected plane. A whole-body motion control framework (Jacobian-based prioritized task space control scheme) tracks the task space trajectories and generates the appropriate joint level command for each state. The joint level commands are tracked by local high gain PD controllers. This framework produces the desired whole-body motion during each state while satisfying higher priority constraints. Gait termination is accomplished by controlling the swing foot position to track the FPE point on the ground along the selected plane. The proposed control strategy is verified in simulation and experiments. A parallel hardware-in-the-loop (HIL) testing environment is developed for the physical lower body humanoid robot. The motion control framework and joint dynamics used in the proposed walking control strategy are verified through HIL experiments.

The effects of multiple sclerosis (MS) on the central nervous system often manifest as abnormalities in gait kinematics. Clinically practical, valid, and reliable measures of gait kinematics are necessary to address research and clinical questions about MS. Wireless flexible electrogoniometry (EG) is a clinically practical measure of joint angles. The GAITRite walkway system is a clinically practical, valid and reliable measure of temporal and spatial gait characteristics. The overall objective of this two-study research project was to explore whether these clinically practical measures of gait kinematics can be used to accurately detect gait abnormalities in people with multiple sclerosis. Study 1 examined the reliability and validity of EG and Study 2 examined the gait kinematics of people with MS (PWMS) using EG and GAITRite. For Study 1, angle at initial contact and total joint excursion were measured by EG at both the knee and ankle while ten healthy adults walked at a self-selected comfortable speed. Measurements were repeated for two testers and two visits to assess reliability. The same variables were measured concurrently with three-dimensional motion analysis (3D) to assess validity. For all variables, reliability was good as indicated by low measurement error and validity was good as indicated by association and agreement of EG with 3D. For Study 2, the same joint angles, along with speed, cadence, step length, stride length, stance duration and double support duration were assessed for six PWMS and six controls without MS. PWMS showed significantly reduced speed, cadence, and ankle excursion and increased stance and double support duration as previously shown with 3D. Spasticity and/or instability may lead to these kinematic gait abnormalities in PWMS; however, reduced velocity may confound this interpretation by affecting the other observed gait abnormalities. Further research about the determinants of gait dysfunction in PWMS is required. EG and GAITRite are clinically practical, valid and reliable measures of gait kinematics and should be included in further clinic-based research to determine which kinematic gait abnormalities are causes and which are effects of the observed decrease in gait speed in PWMS.

This thesis sets up terrain parameters and locomotion strategies of a hexapod robot walking on variable and discontinuous terrain. Walking on this kind of terrain is the greatest advantage of legged robots compared with wheeled robots. First, establish a randomly distributed parameterized terrain. Second, set up morphological parameters and dimension parameters of the robot. Third, build kinematic model and generate continuous gaits of the robot, including crab gaits and turning gaits. The locomotion strategy can determine every AEP ,PEP and stride depending on terrain. Finally, verify the strategy through computer programming and find shorter path by calculating if foothold is available in advance. Because of applying randomly distributed parameterized terrain, in addition to describing the terrain more comprehensively, the terrain parameters can be adjusted easily according to different needs. This research will bring about more applications and developments of legged robots.

Walking machines may not be more common or faster than the transportations with wheels. It can¡¦t be ignored in the occasions of unknown terrain. This paper is going to discuss about how a walking machine get faster and be static stable. When the quadrupeds walk toward, the wide won¡¦t be changed. So that, longitudinal stability margin can take the place of stability margin to simplify gait problems. Meanwhile we can get the optimal gait. In the past researches, there is only one kind of walking type will be discussed in one time. This is because there are not so many relationships between different kinds of movement. If we take one step ahead to discuss the optimal gait, it will be more difficult. If there was a way to get into optimal gait from random initial position, we can connect one movement with the other. The velocity was constrained while the quadruped modal has had been made since 1968 by McGhee. We will try to change the working area to approve the performance. As to the researches of multi-legs walking machine, most of them talk about quadrupeds and hexapods. it will be less if the more legs we are talked about. To maintain stable tread, a walking machine request four legs at least. We can regard a quadruped as a unit, and divide a multi-leg working machine in to many quadrupeds. By using the method of quadruped analysis, we can simplify multi-legs gait algorithm problems.

Legged robots are much difficult to design and control than wheeled robots. However, one of advantages of the legged robots is that they are move adaptable to rough terrains and the task of stepping over obstacles. The gait algorithm of a robot is an important job before components the configuration of the body and each leg. The main purpose of this thesis is to discuss leg failure in gait planning procedure for multi-legged robots with symmetric structures. The legs discussed herein are in the form of an articulated arm with three revolute joints. Various effects on motion characteristics due to different leg faults, such as robot¡¦s walking efficiency and stability are also investigated. On extreme conditions, the robot will cease to walk after a leg failure. In this work a scheme is proposed to transform the scrambled leg pattern to a better or even optimum configuration. This leg switching scheme can improve the stability of the robot when problematic legs are disconnected from the body.