Pneumatic-driven jumping robot with anthropomorphic muscular skeleton structure

Human muscular skeleton structure plays an important role for adaptive locomotion. Understanding of its mechanism is expected to be used for realizing adaptive locomotion of a humanoid robot as well. In this paper, a jumping robot driven by pneumatic artificial muscles is designed to duplicate human leg structure and function. It has three joints and nine muscles, three of them are biarticular muscles. For controlling such a redundant robot, we take biomechanical findings into account: biarticular muscles mainly contribute to joint coordination whereas monoarticular muscles contribute to provide power. Through experiments, we find (1) the biarticular muscles realize coordinated movement of joints when knee and/or hip is extended, (2) the extension of the ankle does not lead to coordinated movement, and (3) we can superpose extension of the knee with that of the hip without losing the joint coordination. The obtained knowledge can be used not only for robots, but may also contribute to understanding of adaptive human mechanism.     

Time-optimal motions of robots in assembly tasks

For a cylindrical, and a spherical robot, and a robot with a horizontal articulated arm with two links, time-optimal unconstrained trajectories for arbitrary fixed initial and final positions are calculated. The exact equations of motion are utilized. The controls (torques and forces) are limited. The general structure of the optimal solution is discussed and explained physically for each robot. The importance of such analyses during the mechanical design of a robot is pointed out. The reduction of the duration of an optimal motion, compared to more straightforward and natural ones, and hence the increase of the productivity of the robot in an assembly cycle can be considerable. The numerical examples include the "Automelec ACR" and the "IBM 7535 B 04" robots.     

Redundancy problem in writing: from human to anthropomorphic robotarm

This paper presents the analysis of motion of a redundant anthropomorphic arm during the writing. The modeling is based on the separation of the prescribed movement into two motions: smooth global, and fast local motion, called distributed positioning (DP). The distribution of these motions to arm joints is discussed. It is based on the inertial properties and actuation capabilities of joints. The approach suggested allows unique solution of the inverse kinematics of redundant mechanisms such as human arm and anthropomorphic robot arm. Distributed positioning is an inherent property of biological systems. Humans, when writing, as shown in literature and in our earlier work control their proximal joints, while the movement of distal joints follow them (synergy). To enhance capabilities of robots, new control schema are necessary. We show that robot control can be improved if it is biological analog. The major aim of this study is to promote such a hypothesis by using anthropomorphic robot arm in writing as an example.     

Design and motion analysis of vibration-driven small robot Rizeh

Vibration mechanism is good candidates to be used as actuation system in small robots. However, mini fabrication of small electrical and mechanical drives is a challenging issue. Moreover, no analytical model for motion analysis of vibration driven robots is devised. In this paper, a small robot is developed. To setup a low-cost robot, cell phone vibrators are employed as actuation mechanism. Motion principle of the robot is analytically obtained and appropriate mechanical and electronic derives are designed. Some technical tips are employed to reduce the size of the robot. The obtained model was evaluated by simulations in MSC.ADAMS as well as some standard experiments on a real robot named Rizeh. Moreover, the robot is tested in a line following task, as a typical task for mobile robots.     

Human direct teaching of industrial articulated robot arms based on force-free control

Force-free control produces motion in a robot arm as if it were under conditions with no gravity and no friction. In this study, a method of force-free control is proposed for industrial articulated robot arms. The force-free control proposed was applied to the direct teaching of industrial articulated robot arms in that the robot arm was moved by direct human force. Generally, the teaching of industrial articulated robot arms is carried out using operational equipment called a teach-pendant. Smooth teaching can be achieved if direct teaching is applicable. The force-free control proposed enables humans to teach industrial articulated robot arms directly. The effectiveness of force-free control was confirmed by experimental work on an articulated robot arm with two degrees of freedom. This work was presented in part at the Fifth International Symposium on Artificial Life and Robotics, Oita, Japan, January 26–28, 2000     

Performance analysis of a new energy-efficient variable supply pressure electro-hydraulic motion control method

Electro-hydraulic actuation is used in many motion control applications due to its high power density, excellent dynamic response and good durability. However fluid power actuation has been shown to be very energy inefficient, with an average efficiency for fluid power systems across all industries of 22% in the USA. This is a very significant problem, given that 3% of the energy used by mankind is transmitted in this way.The key challenge for researchers is to reduce energy losses in hydraulic actuation systems without increasing weight, size, and noise, and without reducing speed of response. Conventional high performance electro-hydraulic motion control systems use a fixed supply pressure with valve-controlled actuators (FPVC). This is inherently inefficient due to the need to use a valve to throttle the flow required by each actuator in the system down to match its load pressure. In this paper, a new load-prediction based method is proposed, in which the supply pressure is varied to track the pressure required by any actuator branch. By implementing this model-based approach using a high response servomotor-driven pump, it is shown that the dynamic response remains excellent. The load model not only allows feedforward control for servomotor speed based on the motion demand, but also feedforward for the control valves to supplement conventional proportional-integral feedback control.The new variable supply pressure valve-controlled (VPVC) method is investigated in simulation and experimentally using a two-axis hydraulic robot arm supplied by an axial piston pump. The performance has been rigorously compared with the same robot arm using a fixed supply pressure and proportional-integral joint position control. Experimental results showed that up to 70% hydraulic power saving was achieved, and that the dynamic tracking errors for VPVC were about half that for FPVC as a result of using feedforward control.     

Automation of surface finishing processes

The development of robots capable of interacting dynamically with the environment has proven to be a difficult task. Since a majority of manufacturing tasks require interaction of robots with their environment, this has become an important focus for research in the industry. Solutions both to specific manufacturing operations and to the theoretical body of knowledge within the industry are extremely important. The interaction of the robot with its environment is investigated in this paper for the configuration of a quick actuator and sensor attached to the robot tool. This configuration has been tested in an industrial application for Steinway & Sons, the world renowned piano manufacturer, specifically for the automation of the labor-intensive rubbing and finishing operations. The robot architecture utilizes a combination of macro-micro manipulator to improve its response time. A quick actuator added to the end of the robot arm is the micromanipulator, and the robot arm is the macromanipulator. Force and impedance control laws are executed concurrently by two separate controllers to control the quick actuator and the robot arm respectively. The experimental system proves the ability of this configuration to follow the complex contour of a grand piano rim and to exert a given force while rubbing its surface.     

Rapid and Cheap Learning by Exploiting Biarticular Muscles — A Case Study With a Two-Dimensional Serpentine Robot

This study is intended to deal with the interplay between control and mechanical systems, and to discuss the 'brain–body interaction as it should be', particularly from the viewpoint of learning. To this end, we have employed a decentralized control of a two-dimensional serpentine robot consisting of several identical body segments as a practical example. The preliminary simulation results derived indicate that the convergence of decentralized learning of locomotion control can be significantly improved, even with an extremely simple learning algorithm, i.e., a gradient method, by introducing biarticular muscles which induce long-distant physical interaction between the body segments compared to the one only with monoarticular muscles. This strongly suggests the fact that a certain amount of computation should be offloaded from the brain into its body, which allows robots to emerge various with interesting functionalities.     

Non-linear phase different control for precise output force of bi-articularly actuated manipulators

Bi-articular actuators – actuator spanning two joints – play fundamental role in robot arms designed under the human musculoskeletal actuation paradigm. Unlike kinematic redundancy, actuator redundancy resulting from bi-articular actuation brings advantages such as increasing stability, reducing link's inertia, and decreasing non-linearity of the end-effector force with respect to the force direction. The traditional phase different control (PDC) resolves actuator redundancy on the basis of a linearized model derived from measured human muscle activity. Such linear model produces a non-zero error in calculation between a desired output force and necessary inputs. In this paper, the non-linear phase different control (NLPDC) is proposed to resolve actuator redundancy with no error. The maximum end-effector force of BiWi, bi-articularly actuated, and wire-driven arm, is measured using both PDC and NLPDC. When the robot arm moves towards singular configurations, the measured error in output force remains within the modeling error if using NLPDC, while such error increases significantly for PDC. Furthermore, unlike PDC, the proposed NLPDC allows design of joint stiffness and torque independently, reduction of necessary total muscle input force, and precise calculation of maximum output force.     

A Framework for Augmented Reality using Non-Central Catadioptric Cameras

This paper proposes a strategy for a group of swarm robots to self-assemble into a single articulated(legged) structure in response to terrain difficulties during autonomous exploration. These articulated structures will have several articulated legs or backbones, so they are well suited to walk on difficult terrains like animals. There are three tasks in this strategy: exploration, self-assembly and locomotion. We propose a formation self-assembly method to improve self-assembly efficiency. At the beginning, a swarm of robots explore the environment using their sensors and decide whether to self-assemble and select a target configuration from a library to form some robotic structures to finish a task. Then, the swarm of robots will execute a self-assembling task to construct the corresponding configuration of an articulated robot. For the locomotion, with joint actuation from the connected robots, the articulated robot generates locomotive motions. Based on Sambot that are designed to unite swarm mobile and self-reconfigurable robots, we demonstrate the feasibility for a varying number of swarm robots to self-assemble into snake-like and multi-legged robotic structures. Then, the effectiveness and scalability of the strategy are discussed with two groups of experiments and it proves the formation self-assembly is more efficient in the end.     

Dynamic path tracking control of a vehicle on slippery terrain

This paper deals with accuracy and reliability for the path tracking control of a four wheel mobile robot with a double-steering system when moving at high dynamics on a slippery surface. An extended kinematic model of the robot is developed considering the effects of wheel–ground skidding. This bicycle type model is augmented to form a dynamic model that considers an actuation of the four wheels. Based on the extended kinematic model, an adaptive and predictive controller for the path tracking is developed to drive the wheels front and rear steering angles. The resulting control law is combined with a stabilization algorithm of the yaw motion which modulates the actuation torque of each four wheels, on the basis of the robot dynamic model. The global control architecture is experimentally evaluated on a wet grass slippery terrain, with speeds up to 7 m/s. Experimental results demonstrate enhancement of tracking performances in terms of stability and accuracy relative to the kinematic control.     

Physics-based simulation for manual robot guidance—An eRobotics approach

Manual robot guidance is an intuitive approach to teach robots with human's skills in the loop. It is particularly useful to manufacturers because of its high flexibility and low programming effort. However, manual robot guidance requires compliance control that is generally not available in position-controlled industrial robots. We address this issue from a simulation-driven approach. We systematically capture the interactive dynamic behavior of intelligent robot manipulators within physics-based virtual testbeds, regardless of the type of application. On this basis, we develop structures to equip and employ simulated robots with motion control capabilities that include soft physical interaction control driven in real-time with real external guidance forces. We then transfer the virtual compliant behavior of the simulated robots to their physical counterparts to enable manual guidance. The simulator provides assistance to operators through timely and insightful robot monitoring, as well as meaningful performance indexes. The testbed allows us to swiftly assess guidance within numerous interaction scenarios. Experimental case studies illustrate the practical usefulness of the symbiotic transition between 3D simulation and reality, as pursued by the eRobotics framework to address challenging issues in industrial automation.     

Estimation of physical interaction between a musculoskeletal robot and its surroundings

Recently, robots are expected to support our daily lives in real environments. In such environments, however, there are a lot of obstacles and the motion of the robot is affected by them. In this research, we develop a musculoskeletal robotic arm and a system identification method for coping with external forces while learning the dynamics of complicated situations, based on Gaussian process regression (GPR). The musculoskeletal robot has the ability to cope with external forces by utilizing a bio-inspired mechanism. GPR is an easy-to-implement method, but can handle complicated prediction tasks. The experimental results show that the behavior of the robot while interacting with its surroundings can be predicted by our method.     

三自由度苹果采摘机器人本体设计

目前绝大部分应用在水果采摘上的关节型机器人控制复杂,成本高,而且采摘效率低,设计结构简单的采摘机器人是研究的重点。针对苹果种植的园艺特点和关节型采摘机械臂的不足,设计了一套基于圆柱坐标的三自由度苹果采摘机器人本体结构。控制系统采用基于PC&MP2100的分布式控制方案,阐明了机器人作业流程,编写了采摘控制程序,控制中引入模糊PID和偏差耦合同步控制方法,并基于C#,开发了人机交互界面。在实验室对机械臂进行了单轴调试、多轴同步调试、运动耗时和定位精度试验,结果表明采摘机械臂单次运动时间平均为6.619 s,平均运动误差值只有4.929 mm,相比关节型机械臂减少了耗时,降低了成本并且提高了定位精度和采摘效率。     

Modified PID Control of a Single-Link Flexible Robot

The use of flexible links in robots has become very common in different engineering fields. The issue of position control for flexible link manipulators has gained a lot of attention. Using the vibration signal originating from the motion of the flexible-link robot is one of the important methods used in controlling the tip position of the single-link arms. Compared with the common methods for controlling the base of the flexible arm, vibration feedback can improve the use of the flexible-link robot systems. In this paper a modified PID control (MPID) is proposed which depends only on vibration feedback to improve the response of the flexible arm without the massive need for measurements. The arm moves horizontally by a DC motor on its base while a tip payload is attached to the other end. A simulation for the system with both PD controller and the proposed MPID controller is performed. An experimental validation for the control of the single-link flexible arm is shown. The robustness of the proposed controller is examined by changing the loading condition at the tip of the flexible arm. The response results for the single-link flexible arm are presented with both the PI and MPID controller used. A study of the stability of the proposed MPID is carried out.     

Stability and joint stiffness analysis of legged robot’s periodic motion driven by McKibben pneumatic actuator

A McKibben-type pneumatic actuator is widely used as a convenient actuator for a robot with a simple actuator model and a simple control method. However, the effect of its characteristics on the stability of robot motion has not been sufficiently discussed. The purpose of our research is to analyze the influence that the various characteristics of a McKibben pneumatic actuator has on the stability of movements generated by the actuator. In this study, we focus on a periodic motion, which is one of the common movements of robots. We introduce a stability criterion for periodic motion similar to our previous work, in which stability of musculo-skeletal system was discussed, and show that the criterion is always satisfied. Next, we focus on a redundancy of air pressure inputs. As one of application of the redundancy, we investigate the joint stiffness of a robot and propose a design procedure of inputs based on a reference period trajectory and the desired joint stiffness. The stability analysis and design of joint stiffness are verified not only through numerical simulations but also through experiments with a developed 1-DOF legged robot.     

A one linear actuator hopping robot: modeling and control

This paper addresses the modeling and control design of a one linear actuator hopping robot. The robot consists of a body and a leg, which are in contact with a sufficiently wide horizontal ground surface; both are fixed rigidly. Force actuation affects the angle of the body by a force couple that arises due to the mass of the body, as well as the length of the leg; hence both the angular velocity of the body and height of a jump can be controlled by only one actuator. Since the aim of this study is to achieve continuous hopping motion while keeping the system as simple as possible, an ON-OFF actuator is employed. Hence, we consider utilizing the thrust timing of the actuator—when robot is in the stance phase—to control the gait. For better stability of the hopping motion, optimization of mechanical parameters was made possible by evaluating the numerically obtained transition map, which contains a transition from one standard position to the next. The system is considered as a discrete system, in which one cycle of motion is regarded as one sampling interval. Finally, a control system was designed in which, by simulation, the continuous hopping gait was realized.     

Motion coordination and reactive control of autonomous multi-manipulator systems

The emerging field of service robots demands new systems with increased flexibility. The flexibility of a robot system can be increased in many different ways. Mobile manipulation—the coordinated use of manipulation capabilities and mobility—is an approach to increase robots flexibility with regard to their motion capabilities. Most mobile manipulators that are currently under development use a single arm on a mobile platform. The use of a two-arm manipulator system allows increased manipulation capabilities, especially when large, heavy, or non-rigid objects must be manipulated. This article is concerned with motion control for mobile two-arm systems. These systems require new schemes for motion coordination and control. A coordination scheme called transparent coordination is presented that allows for an arbitrary number of manipulators on a mobile platform. Furthermore, a reactive control scheme is proposed to enable the platform to support sensor-guided manipulator motion. Finally, this article introduces a collision avoidance scheme for mobile two-arm robots. This scheme surveys the vehicle motion to avoid platform collisions and arm collisions caused by self-motion of the robot. © 1996 John Wiley & Sons, Inc.     

WALK‐MAN: A High‐Performance Humanoid Platform for Realistic Environments

In this work, we present WALK‐MAN, a humanoid platform that has been developed to operate in realistic unstructured environment, and demonstrate new skills including powerful manipulation, robust balanced locomotion, high‐strength capabilities, and physical sturdiness. To enable these capabilities, WALK‐MAN design and actuation are based on the most recent advancements of series elastic actuator drives with unique performance features that differentiate the robot from previous state‐of‐the‐art compliant actuated robots. Physical interaction performance is benefited by both active and passive adaptation, thanks to WALK‐MAN actuation that combines customized high‐performance modules with tuned torque/velocity curves and transmission elasticity for high‐speed adaptation response and motion reactions to disturbances. WALK‐MAN design also includes innovative design optimization features that consider the selection of kinematic structure and the placement of the actuators with the body structure to maximize the robot performance. Physical robustness is ensured with the integration of elastic transmission, proprioceptive sensing, and control. The WALK‐MAN hardware was designed and built in 11 months, and the prototype of the robot was ready four months before DARPA Robotics Challenge (DRC) Finals. The motion generation of WALK‐MAN is based on the unified motion‐generation framework of whole‐body locomotion and manipulation (termed loco‐manipulation). WALK‐MAN is able to execute simple loco‐manipulation behaviors synthesized by combining different primitives defining the behavior of the center of gravity, the motion of the hands, legs, and head, the body attitude and posture, and the constrained body parts such as joint limits and contacts. The motion‐generation framework including the specific motion modules and software architecture is discussed in detail. A rich perception system allows the robot to perceive and generate 3D representations of the environment as well as detect contacts and sense physical interaction force and moments. The operator station that pilots use to control the robot provides a rich pilot interface with different control modes and a number of teleoperated or semiautonomous command features. The capability of the robot and the performance of the individual motion control and perception modules were validated during the DRC in which the robot was able to demonstrate exceptional physical resilience and execute some of the tasks during the competition.     

A U-shaped actuation system for dual-stage actuators used in hard disk drives

In this paper, we propose an actuation system, called U-shaped actuation, for dual-stage actuator to suppress the arm mode flutter. We manufactured an actuator using this actuation method and measured the frequency response. We found that the frequency response had an in-phase arm mode frequency and that there was little difference between each head at arm sway and suspension sway mode. Next, we designed a controller and compared its sensitivity function with that of conventional actuation. By applying stabilizing control to the in-phase arm mode, NRRO of the arm flutter of the outer and inner arms was suppressed by 10.9 and 13.2?%, respectively.