Nut Unfastening by Robotic Surface Exploration

In this paper, we present a novel concept and primary investigations regarding automated unfastening of hexagonal nuts by means of surface exploration with a compliant robot. In contrast to the conventional industrial approaches that rely on custom-designed motorised tools and mechanical tool changers, we propose to use robot fingers to position, grasp and unfasten unknown random-sized hexagonal nuts, which are arbitrarily positioned in the robot’s task space. Inspired by how visually impaired people handle unknown objects, in this work, we use information observed from surface exploration to devise the unfastening strategy. It combines torque monitoring with active compliance for the robot fingers to smoothly explore the object’s surface. We implement a shape estimation technique combining scaled iterative closest point and hypotrochoid approximation to estimate the location as well as contour profile of the hexagonal nut so as to accurately position the gripper fingers. We demonstrate this work in the context of dismantling an electrically driven vehicle battery pack. The experiments are conducted using a seven degrees of freedom (DoF)–compliant robot fitted with a two-finger gripper to unfasten four different sized randomly positioned hexagonal nuts. The obtained results suggest an overall exploration and unfastening success rate of 95% over an average of ten trials for each nut.

An Integrated Compensation Method for the Force Disturbance of a Six-Axis Force Sensor in Complex Manufacturing Scenarios

As one of the key components for active compliance control and human–robot collaboration, a six-axis force sensor is often used for a robot to obtain contact forces. However, a significant problem is the distortion between the contact forces and the data conveyed by the six-axis force sensor because of its zero drift, system error, and gravity of robot end-effector. To eliminate the above disturbances, an integrated compensation method is proposed, which uses a deep learning network and the least squares method to realize the zero-point prediction and tool load identification, respectively. After that, the proposed method can automatically complete compensation for the six-axis force sensor in complex manufacturing scenarios. Additionally, the experimental results demonstrate that the proposed method can provide effective and robust compensation for force disturbance and achieve high measurement accuracy.

Design, analysis & testing of an enhanced radial-axial hybrid compliant deburring tool

This thesis will discuss the development of a radial actuator incorporated into a deburring tool. Gas turbine engine deburring is complex; this requires the tooltip to maintain active compliance in three degrees of freedom. This can be achieved through the use of a rotating action plane so that only radial and axial actuation is required. A proposed enhanced radial actuator has been made that utilizes the action plane model and fulfill the requirements for precision deburring of gas turbine engine components. The enhanced radial actuator was designed using four silicone rubber pneumatic diaphragms. The diaphragms were modelled using a finite element method and applying an Arruda-Boyce material model to the mesh. The stiffness behaviour was analyzed and compared to data from previous research completed on radial actuation within an action plane. The stiffness behaviour was determined to be superior and significantly improved as it could be reliably predicted.

Design, analysis & testing of an enhanced radial-axial hybrid compliant deburring tool

This thesis will discuss the development of a radial actuator incorporated into a deburring tool. Gas turbine engine deburring is complex; this requires the tooltip to maintain active compliance in three degrees of freedom. This can be achieved through the use of a rotating action plane so that only radial and axial actuation is required. A proposed enhanced radial actuator has been made that utilizes the action plane model and fulfill the requirements for precision deburring of gas turbine engine components. The enhanced radial actuator was designed using four silicone rubber pneumatic diaphragms. The diaphragms were modelled using a finite element method and applying an Arruda-Boyce material model to the mesh. The stiffness behaviour was analyzed and compared to data from previous research completed on radial actuation within an action plane. The stiffness behaviour was determined to be superior and significantly improved as it could be reliably predicted.

Terrain classification and adaptive locomotion for a hexapod robot Qingzhui

Legged robots have potential advantages in mobility compared with wheeled robots in outdoor environments. The knowledge of various ground properties and adaptive locomotion based on different surface materials plays an important role in improving the stability of legged robots. A terrain classification and adaptive locomotion method for a hexapod robot named Qingzhui is proposed in this paper. First, a force-based terrain classification method is suggested. Ground contact force is calculated by collecting joint torques and inertial measurement unit information. Ground substrates are classified with the feature vector extracted from the collected data using the support vector machine algorithm. Then, an adaptive locomotion on different ground properties is proposed. The dynamic alternating tripod trotting gait is developed to control the robot, and the parameters of active compliance control change with the terrain. Finally, the method is integrated on a hexapod robot and tested by real experiments. Our method is shown effective for the hexapod robot to walk on concrete, wood, grass, and foam. The strategies and experimental results can be a valuable reference for other legged robots applied in outdoor environments.

Controllable Height Hopping of a Parallel Legged Robot

Legged robots imitating animals have become versatile and applicable in more application scenarios recent years. Most of their functions rely on powerful athletic abilities, which require the robots to have remarkable actuator capacities and controllable dynamic performance. In most experimental demonstrations, continuous hopping at a desired height is a basic required motion for legged robots to verify their athletic ability. However, recent legged robots have limited ability in balance of high torque output and actuator transparency and appropriate structure size at the same time. Therefore, in our research, we developed a parallel robot leg using a brushless direct current motor combined with a harmonic driver, without extra force or torque sensor feedback, which uses virtual model control (VMC) to realize active compliance on the leg, and a whole-leg control system with dynamics modeling and parameter optimization for continuous vertical hopping at a desired height. In our experiments, the robot was able to maintain stability during vertical hopping while following a variable reference height in various ground situations.

Expert endorsement and the legitimacy of public policy. Evidence from Covid19 mitigation strategies.

During a pandemic, the government requires active compliance by citizens. While these demands can be enforced with rewards and punishments, legitimacy allows the government to achieve the same results with greater cost effectiveness. In this article, we measure revealed legitimacy through support of three potential mitigation strategies against Covid19, when they are defended using expert endorsement, consultation by civil society, and mediation between opposing interests. We elicit approval of the supporting arguments and of the communication strategy. Our methodological choice was to randomly assign participants to either a non-conflicting priming or to one that emphasizes the risks involved, (e.g. connection between health and economy, uncertainty, and economic costs). The data come from an online experiment we conducted as part of a longitudinal study of several countries. The countries included are Italy, Spain, and the United Kingdom. The results show that the support of experts in non-controversial domains is preferred (consensus of value, low uncertainty, diffuse rents). Contrary to our hypotheses, we found that citizen deliberation is not preferred under high epistemic uncertainty, and mediation is either indifferent or not preferred under conflict of value and conflict of interest.