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The modulation of joint stiffness is a crucial mechanism that allows humans, and other vertebrates, to perform stable and efficient locomotion. Compliant actuation is an emerging branch of robotics, which aims to mimic the biological elastic properties of muscle fibers and series-elastic tendon structures. This paper presents the mechanical design and real prototype of a compliant 2-Degrees of Freedom...
It is well-known that the walking gait for quadruped robots has great potential to travel over rough terrain because of its higher flexibility and better environment adaptability. This paper presents a control framework for a quadruped robot walking over rough terrain, which includes such features: First, a preview controller is designed to create an appropriate body trajectory to realize the desired...
Ankle Foot Orthoses is a supportive equipment attached to the lower part of the leg to support patient's walking posture, gait. It has been developed for several years using many kinds of actuator that can be controlled electronically. In this paper, a controller development by experiment for Passive Control Ankle Foot Orthoses (PICAFO) is presented. A Fuzzy Logic Controller is proposed to control...
We present a set of modular series-elastic actuators (SEAs) that allow rapid and robust prototyping of mobile legged robots. The SEA modules were originally developed for a snake robot, SEA Snake, and have recently been reconfigured into Snake Monster, a multi-modal walking robot that can be easily adapted to hexapod, quadruped, and biped configurations. The use of SEAs allows the implementation of...
Animals and robots balance dynamically by placing their feet into proper ground targets. While foot placement controls exist for both fully robotic systems and powered prostheses, none enable the dynamism and reactiveness of able-bodied humans. A control approach was recently developed for an ideal double pendulum dynamical system that places feet into ground targets for a wide range of initial conditions...
The objective of this work is to achieve disturbance rejection and constant orientation of the trunk of a multi-legged robot. This is significant when payloads (such as cameras, optical systems, armaments) are carried by the robot. In particular, this paper presents an application of an on-line learning method to actively correct the open-loop gait generated by a central pattern generator (CPG) or...
We propose a novel control framework to demonstrate a unique foot tilting maneuver based on ankle torque control for humanoid balance recovery. The framework consists of the variable impedance regulation at the center of mass of the robot based on the ankle torque control, the virtual stoppers to prevent over tilting of the feet, and the body attitude control. The scope of our paper focuses on the...
Nowadays, a comfortable ankle prosthesis with natural walking gait for the amputee has become an important requisite. In this paper, a new kind of active ankle prosthesis is presented, which can not only help amputees walk naturally, but also reduce energy consumption by recycling. Firstly, the structure of ankle prosthesis was proposed. And then, dynamic simulation and structure parameters optimization...
This paper describes a finite state machine to control an ankle-foot prosthesis with two degrees of freedom (DOF) in the sagittal and frontal planes. Strain gauges were installed in the foot to provide ground reaction torques feedback for impedance and admittance controllers to be used at heel-strike and push-off of the gait, respectively. The quasi-static stiffness of the ankle with the active control...
In this paper, we propose an Energy based Fall Prediction (EFP) which observes the real-time balance status of a humanoid robot during standing. The EFP provides an analytic and quantitative measure of the level of balance. Both simulation and experimental studies were conducted and compared with the previously proposed indicators, such as Capture Point (CP) and Foot Rotation Indicator (FRI). The...
Robotic prostheses can improve walking performance for amputees, but prescription of these devices has been hindered by their high cost and uncertainty about the degree to which individuals will benefit. The typical prescription process cannot well predict how an individual will respond to a device they have never used because it bases decisions on subjective assessment of an individual's current...
Collapsible leg spines found on insects and spiders provide a passive mechanism for increased traction while running over complex terrain. In this paper we use this architectural advantage as biological inspiration to increase the useful work in pulling a load with a VelociRoACH, a high speed terrestrial robot. These spines exhibit anisotropic properties in the fore-aft and lateral directions, with...
In our previous work, we introduced a new gait for humanoid robots called Ski-Type walking to improve stability performance for rough terrain walking. By the arms holding two canes to assist walking, the humanoid robot benefits from enlarged stability margin. With canes and feet touching the ground, a closed-chain system is formed where force/torque distribution among the canes and feet is not unique...
Terrain compliance is a critical parameter for the performance of legged locomotion. In this work, a single actuator monopod robot hopping on rough compliant terrain is considered. Based on our controller for flat compliant terrains, this paper introduces the necessary modifications, which allow the robot to tackle the disturbance of small inclinations. Using the developed method, the robot is examined...
For legged devices, their ability of carrying payload is a necessity for a wide range of tasks. In this paper, we present a new approach of carrying payload by using a parallel elastic mechanism, which is able to carry payloads of at least 3 times of its bodyweight. Although the robot has no sensory feedback and consists of only two rigid bodies and one spring loaded joint, it is able to achieve efficient...
This paper presents the design of a locomotion interface for gait simulation and interaction with a virtual environment. The proposed mechanical interface is based on two planar two-degree-of-freedom belt-driven mechanisms which fully decouple the vertical and horizontal motion of two supporting footplates. Force sensors are mounted under the footplates in order to move the end effectors according...
Background Stress occurring at the feet while wearing footwear is often determined using pressure measurement systems. However, other forms of stress, such as bending, torsional and shear loadings, cannot be detected in shoes during day-to-day activities. Nevertheless, the detection of these types of stresses would be helpful for understanding the mechanical aspects of various kinds of hard and soft...
This paper proposes a new generic strategy to investigate the dynamic limits of the humanoid robot HRP-2 based on whole body optimal control optimization. In this study we exploit the intuitive access to complex motion characteristics, given by optimal control, to effectively resolve a major technical coupling effect, namely between the ankle elasticity and the stabilizing algorithms. Control efforts...
One popular approach to controlling humanoid robots is through inverse kinematics (IK) with stiff joint position tracking. On the other hand, inverse dynamics (ID) based approaches have gained increasing acceptance by providing compliant motions and robustness to external perturbations. However, the performance of such methods is heavily dependent on high quality dynamic models, which are often very...
Biped Robots are a class of legged robots, which should work in various environments such as flat or uneven terrain. To walk on different surfaces, it should be adaptable to the variations on the ground with a flexibility in foot movement to maintain its stability. Zero Moment Point (ZMP) is a technique used to ensure dynamic stability. ZMP should be within the support polygon for a robot to be stable...
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