Whole-Body Control (WBC) has emerged as an important framework in locomotion control for legged robots. However, most WBC frameworks fail to generalize beyond rigid terrains. Legged locomotion over ...soft terrain is difficult due to the presence of unmodeled contact dynamics that WBCs do not account for. This introduces uncertainty in locomotion and affects the stability and performance of the system. In this article, we propose a novel soft terrain adaptation algorithm called STANCE: Soft Terrain Adaptation and Compliance Estimation. STANCE consists of a WBC that exploits the knowledge of the terrain to generate an optimal solution that is contact consistent and an online terrain compliance estimator that provides the WBC with terrain knowledge. We validated STANCE both in simulation and experiment on the Hydraulically actuated Quadruped (HyQ) robot, and we compared it against the state-of-the-art WBC. We demonstrated the capabilities of STANCE with multiple terrains of different compliances, aggressive maneuvers, different forward velocities, and external disturbances. STANCE allowed HyQ to adapt online to terrains with different compliances (rigid and soft) without pretuning. HyQ was able to successfully deal with the transition between different terrains and showed the ability to differentiate between compliances under each foot.
Legged robots must contend with challenges like load fluctuations, external forces, and modeling errors in their working environment, all of which can lead to inaccuracies in the model predictive ...control (MPC) state mapping equation. Neglecting these issues can result in deviation from the predefined trajectory, and even instability. In this article, we propose a novel MPC strategy for legged robots that enables dynamic correction of the system model and enhancing computational robustness. First, a state feedback MPC controller is proposed. Unlike prior works, we reconstruct the original nonlinear model with uncertainties as a linear model with time-varying disturbances. Subsequently, we design a closed-loop state observer to approximate the reconstructed model and employ it as the benchmark for prediction in MPC. We utilized the Lyapunov function to demonstrate that this method can ensure the ultimate uniform boundedness of state estimation errors. Second, we cascaded a whole-body controller with computational robustness as a compensatory controller for the MPC. Finally, extensive experiments on the biped robot BRAVER validated the proposed framework in both simulation and physical prototype.
Whole-body control (WBC) has emerged as an important framework in manipulation for mobile manipulators. However, most existing WBC frameworks require known dynamics. Considering whole-body ...manipulation and optimization with unknown dynamics, this article presents the WBC of a nonholonomic mobile manipulator using model predictive control (MPC) and fuzzy logic system. First, by constructing a dynamics-based feedback linearized robotic multi-input-multi-output (MIMO) system, an MPC-based WBC strategy is proposed for mobile manipulator. Such a strategy can provide the optimal control inputs with the specified optimization index and constraints. Thereafter, a primal-dual neural network effectively addresses the constrained quadratic programming (QP) problem over a finite receding horizon brought by the MPC. Then, in order to convert the intermediate control signals into the optimal control torques that can be executed by actuators, an adaptive FLS is employed to approximate the unknown dynamics. The novel elements of the current design control approach refer to the dynamics-based feedback linearized robotic MIMO system and the combination of an MPC module with an adaptive fuzzy controller. Finally, the trajectory tracking experiments performed on a mobile dual-arm robot demonstrate the effectiveness of the proposed method.
The flexible-joint robot has superior attractive features because of its high mobility, high load ratio, high torque fidelity, robustness for external disturbance, task adaptability, and safety. In ...this article, an autonomous mobile manipulator driven by the designed series elastic actuators is developed. A complete dynamic model of a nonholonomic mobile manipulator including a mobile platform and a manipulator with joint flexibility operating simultaneously is proposed. An integrated whole-body trajectory control framework is proposed for such robot to perform mobile manipulation tasks. Considering the nonholonomic and holonomic constraints in the mobile manipulation, the whole-body dynamics is formulated and reduced. To address the highly nonlinear of the dynamics and model uncertainty, a novel integral Lyapunov function based adaptive neural network control for task tracking under uncertainties of the flexible-joint robot model is proposed. Compared with existing methods, the proposed method provides an alternative for controlling flexible-joint robots. The feasibility of the proposed method is verified by the extensive trajectory tracking experiment results in our developed flexible joint manipulator.
Examination of cognition has historically been approached from language and introspection. However, human language-dependent definitions ignore the evolutionary roots of brain mechanisms and ...constrain their study in experimental animals. We promote an alternative view, namely that cognition, including memory, can be explained by exaptation and expansion of the circuits and algorithms serving bodily functions. Regulation and protection of metabolic and energetic processes require time-evolving brain computations enabling the organism to prepare for altered future states. Exaptation of such circuits was likely exploited for exploration of the organism's niche. We illustrate that exploration gives rise to a cognitive map, and in turn, environment-disengaged computation allows for mental travel into the past (memory) and the future (planning). Such brain-body interactions not only occur during waking but also persist during sleep. These exaptation steps are illustrated by the dual, endocrine-homeostatic and memory, contributions of the hippocampal system, particularly during hippocampal sharp-wave ripples.
Powered exoskeletons have been shown to significantly reduce physical workload during occupational tasks. Due to this they have great potential impact on future labor practices. However, powered ...exoskeleton controllers must first be developed that are able to directly assist with task objectives and truly collaborate with users. To address this need we present a shared autonomy control framework that separates the human and exoskeleton control objectives. This allows for creating a feedback-based exoskeleton controller that will help accomplish the user’s task goals rather than just assisting in specific motions. We introduce Positive Power control for the human-based controller that is designed to allow the human to directly command work that accomplishes the desired task. While a standard robotic controller can be used for the feedback-based control, we introduce ‘acceptance’ as a measure of how well the exoskeleton’s control objective matches the human’s. Both control objectives are implemented in an optimization-based Whole-Body-Control structure. Finally, we introduce a method to update the exoskeleton’s objectives to match the humans’ such that after operating for a time the exoskeleton can learn to assist the user in accomplishing their task. This framework is implemented on a 10-DoF upper-body powered exoskeleton. The results verify that the control framework works as desired and can form a basis for developing extended methods for directly improving cooperative control for powered exoskeletons.
•Whole Body Control for powered exoskeletons balances multiple task objectives.•Shared Autonomy framework seamlessly integrates human and robot control.•User “acceptance” of exoskeleton control objectives enables intuitive task learning.•Positive Power, human-input control provides direct assistance to task accomplishment.•Improved controller design moves towards more effective exoskeleton-human cooperation.
The control of a robot in its task space is a standard approach nowadays. If the system is kinematically redundant with respect to this goal, one can even execute additional subtasks simultaneously. ...By utilizing null space projections, for example, the whole stack of tasks can be implemented within a strict task hierarchy following the order of priority. One of the most common methods to track multiple task-space trajectories at the same time is to feedback-linearize the system and dynamically decouple all involved subtasks, which finally yields the exponential stability of the desired equilibrium. In this article, we provide a hierarchical multi-objective controller for trajectory tracking that ensures both asymptotic stability of the equilibrium and a desired contact impedance at the same time. In contrast to the state of the art in prioritized multi-objective control, feedback of the external forces can be avoided and the natural inertia of the robot is preserved. The controller is evaluated in simulations and on a standard lightweight robot with torque interface. The approach is predestined for precise trajectory tracking where dedicated and robust physical-interaction compliance is crucial at the same time.
In recent years, menopause as a phase of transition has received great media attention in Sweden, not only in terms of the cessation of menstrual periods, but specifi cally with a focus on hormonal ...changes in the longer period of time during which female bodies undergo adjustment. In books such as Hormonstark Hormone strong (2020), Perimenopower (2018) and Livet med klimakteriet Life with Menopause (2020), the stressed reader in mid-career can get knowledge, tips, ideas and inspiring stories about how to deal with the fl uctuating hormones that are said to affect the body during menopause. In this article, we take a poststructuralist feminist perspective on the narratives of hormones and body control in the above mentioned three examples of self-help literature. The aim is to explore how this type of literature represents women’s menopause and hormonal bodies in a broader sense, and how women are in relation to this discourse. The results show that, although hormone narratives may have feminist potential, they primarily represent menopause as an individual rather than a structural matter. The result also display a close resemblance between hormone narratives and contemporary biocapitalism with the aging female body as a lucrative threat.
In recent years, menopause as a phase of transformation has received great media attention in a Swedish context. It is then not only specifically about the time when menstruation ceases – but about a longer period of time when female bodies undergo an adjustment with a focus on hormonal changes. In books such as Hormonstark (Hormone strong) (2020), Perimenopower (2018) and Livet med klimakteriet (Life with Menopause) (2020), the stressed reader in the middle of the career receives knowledge, tips, ideas and inspiring stories about how to deal with the fluctuating hormones that are said to affect the body during menopause. In this article, we start from these books with a poststructuralist feminist perspective on narratives and body control on the hormone stories of self-help literature. The aim is to explore how the literature represents women's menopause and hormonal bodies in a broader sense, and how women are encouraged to act in relation to this. The results show that hormone narratives may have feminist potential, but that they primarily make menopause an individual rather than structural matter. Further, they also reveal a close resemblance between the hormonal narratives and a biocapitalist contemporary, with an aging female body as a lucrative threat.
Balansreceptet Linda Berg; Anna Sofia Lundgren; Maria Jönsson
Kvinder, køn & forskning (Online),
02/2023, Volume:
34, Issue:
2
Journal Article
Peer reviewed
Open access
In recent years, menopause as a phase of transition has received great media attention in Sweden, not only in terms of the cessation of menstrual periods, but specifi cally with a focus on hormonal ...changes in the longer period of time during which female bodies undergo adjustment. In books such as Hormonstark Hormone strong (2020), Perimenopower (2018) and Livet med klimakteriet Life with Menopause (2020), the stressed reader in mid-career can get knowledge, tips, ideas and inspiring stories about how to deal with the fl uctuating hormones that are said to affect the body during menopause. In this article, we take a poststructuralist feminist perspective on the narratives of hormones and body control in the above mentioned three examples of self-help literature. The aim is to explore how this type of literature represents women’s menopause and hormonal bodies in a broader sense, and how women are in relation to this discourse. The results show that, although hormone narratives may have feminist potential, they primarily represent menopause as an individual rather than a structural matter. The result also display a close resemblance between hormone narratives and contemporary biocapitalism with the aging female body as a lucrative threat.
Quadruped robots can mimic animal locomotion mode and have great potential usage in unstructured environments. However, as mobile platforms, quadruped robots often lack manipulation capabilities. In ...this project, we equipped the quadruped robot SDU-ADog with a torque-controlled 6-DOF arm. A novel control framework which combines virtual model control (VMC) and prioritized whole-body control (WBC) for the whole system is proposed in this paper. VMC finds optimal target ground reaction forces while compensating the arm’s inertia, and then makes the robot compliant to external disturbance. Prioritized WBC deals with multiple tasks in an optimal fashion and achieves efficiency and robustness of robot’s locomotion and manipulation. The effectiveness of our framework has been evaluated through a set of robot dynamic simulations conducted in Webots. The robot can finish balance maintaining with moving arm, fixed point tracking while trotting, and locomotion over different obstacles with an end-point task.
•We devise a control framework for legged mobile manipulators which considers the full kinematics and dynamics model of the robot.•We stabilize the robot’s CoM position and orientation by combining VMC and WBC.•We validate the method’s robustness by simulations of fixed-point tracking while trotting over obstacles.•The robustness is further validated by experiments on our robot. The results show that our control frame work is valid and easy to transfer from simulation to reality.
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