Advanced Robotics

Alipour, Khalil; Moosavian, S. Ali A.

doi: 10.1163/156855312X633020pmid: N/A

Abstract In this paper, dynamics, postural stability and control of suspended wheeled mobile manipulators for cooperative heavy object manipulation are elaborated considering the effect of grasping posture. The presented model considers a system equipped with multiple manipulators with flexible suspension, which also contains an accurate nonlinear behavior of the tires. Moreover, it includes the vibratory response of the tires as unsprung masses. Therefore, this is one of the most complete models that have been presented for wheeled mobile manipulators to date. First, based on the Newton–Euler formulation for a chain of rigid bodies, the dynamics model of such complicated systems in three-dimensional maneuvers is developed without considering a nonlinear frictional model of tires, which was verified using the ADAMS multibody simulator. Then, a proper nonlinear friction model is added to the developed dynamics to provide a more complete one. Considering pneumatic tires, the Dugoff tire friction model is adopted to describe the longitudinal and lateral forces produced at the contact patch of the wheels. Using the obtained dynamics along with the moment-height stability measure the effect of frictional effects as well as suspension attributes on the postural stability of such systems are accurately investigated for maneuvers over flat and rough terrains. Finally, the effect of grasping posture and relevant configuration of the robot on the stability of the system is examined during a heavy object manipulation task.

Shen, Tiantian; Chesi, Graziano

doi: 10.1163/156855312X632904pmid: N/A

Abstract This paper proposes a path planning visual servoing strategy for a class of cameras that includes conventional perspective cameras, fisheye cameras and catadioptric cameras as special cases. Specifically, these cameras are modeled by adopting a unified model recently proposed in the literature and the strategy consists of designing image trajectories for eye-in-hand robotic systems that allow the robot to reach a desired location while satisfying typical visual servoing constraints. To this end, the proposed strategy introduces the projection of the available image features onto a virtual plane and the computation of a feasible image trajectory through polynomial programming. Then, the computed image trajectory is tracked by using an image-based visual servoing controller. Experimental results with a fisheye camera mounted on a 6-d.o.f. robot arm are presented in order to illustrate the proposed strategy.

Yamaguchi, Akihiro; Takemura, Kenjiro; Yokota, Shinichi; Edamura, Kazuya

doi: 10.1163/156855312X632913pmid: N/A

Abstract An electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a jet flow (ECF jet) when subjected to high DC voltage. It is known that a strong ECF jet is generated under a non-uniform electric field (e.g., a field with a pair of needle and ring electrodes (a needle–ring electrode pair)). This study introduces the ECF jet to develop a novel flexible robot finger. First, we propose a concept for a novel robot finger. The robot finger mainly consists of a bending actuator, an ECF tank and ECF jet generators, which could be a micro fluid pressure source of the robot finger. Second, we characterize each component of the robot finger (i.e., the bending actuator and the ECF jet generator). We investigate the influences of electrode parameters on ECF jet generator performance in order to design the finger prototype. Finally we clarify the characteristics of the robot finger. The length, the diameter and the mass of the robot finger are 34.2 mm, 12 mm and 3.8 g, respectively. The robot finger can generate a force of 0.28 N and bend approximately 70°.

Jin, Shanhai; Kikuuwe, Ryo; Yamamoto, Motoji

doi: 10.1163/156855312X633011pmid: N/A

Abstract This paper presents a sliding mode filter for removing noise. It effectively removes impulsive noise and highfrequency noise, producing a smaller phase lag than linear filters. In addition, it is less prone to overshoot than previous sliding mode filters and it does not produce chattering. It is computationally inexpensive and thus suitable for real-time applications. The proposed sliding mode filter employs a quadratic surface as its sliding surface, which is designed so that the output converges to the input in finite time when the input value is constant. Its algorithm is derived by using the backward Euler discretization, which can be used to prevent chattering. The effectiveness of the filter was shown by experiments using an ultrasonic sensor and an optical encoder.

Lee, Sang Hyoung; Suh, Il Hong

doi: 10.1163/156855312X633039pmid: N/A

Abstract In this paper, we generate probabilistic affordances to select a dependable behavior based on motivation values. Dependable behavior, in our context, refers to behavior that is situation-adequate as well as goaloriented. The probabilistic affordance is designed as a multilayer naïve Bayesian classifier with respect to uncertainties and reusability. A multilayer naïve Bayesian classifier is a probabilistic model with multiple layers comprising conditional probability tables or probability distributions based on equivalence classes. The affordances consider situation-adequateness in given situations and suggest possibilities of behaviors based on Bayesian inference. In order to select a dependable behavior to achieve a task, the affordances are arranged based on a sequential structure. This is because accomplishing a task usually requires sequentially performed behaviors. Motivation values are generated using the arranged affordances and a motivation value propagation algorithm. A robot selects a dependable behavior based on these motivation values. To validate our proposed methods, we present experimental results of an entertainment robot called AIBO handling three tasks.

Gao, Bingtuan; Xu, Jing; Zhao, Jianguo; Xi, Ning

doi: 10.1163/156855312X633048pmid: N/A

Abstract A special humanoid neck with low motion noise requirements yields a cable-driven parallel mechanism to imitate the rotational motion of a human neck. The fixed base and moving platform of the mechanism are connected by four cables and a column compression spring. The four cables are actuated separately, while the spring can support weight on the moving platform. Although similar mechanisms exist in the literature, the analysis of them is scarce because a flexible spring instead of a rigid kinematic chain is used as the spine. With the spring’s lateral buckling motion, a new approach must be adopted to solve the kinematics. In this paper, we propose a method that combines the kinematics with the statics to solve them simultaneously. The configuration of the moving platform is parameterized with four parameters, one of which is considered as parasitic motion. Using the spring’s lateral buckling equation, we can obtain the parasitic motion and solve the inverse position problem. The optimal design for cable placements is then performed to minimize the actuation force. The method in this paper provides a novel way to analyze parallel mechanisms with a spring spine and it can be applied to other mechanisms with flexible spines.

Courbon, Jonathan; Mezouar, Youcef; Martinet, Philippe

doi: 10.1163/156855312X633057pmid: N/A

Abstract A wide field of view is required for many robotic vision tasks. Such an aperture may be acquired by a fisheye camera, which provides a full image compared to catadioptric visual sensors, and does not increase the size and the weakness of the imaging system with respect to perspective cameras. While a unified model exists for all central catadioptric systems, many different models, approximating the radial distortions, exist for fisheye cameras. It is shown in this paper that the unified projection model proposed for central catadioptric cameras is also valid for fisheye cameras in the context of robotic applications. This model consists of a projection onto a virtual unitary sphere followed by a perspective projection onto an image plane. This model is shown equivalent to almost all the fisheye models. Calibration with four cameras and partial Euclidean reconstruction are done using this model, and lead to persuasive results. Finally, an application to a mobile robot navigation task is proposed and correctly executed along a 200-m trajectory.

Endo, Gen; Hirose, Shigeo

doi: 10.1163/156855312X633066pmid: N/A

Abstract Roller-Walker is a leg–wheel hybrid mobile robot using a passive wheel equipped on the tip of each leg. The passive wheel can be transformed into sole mode by rotating the ankle roll joint when Roller-Walker walks on a rough terrain. This paper discusses the energy efficiency of locomotion in wheeled mode. We define a leg trajectory to produce forward straight propulsion, and discuss the relationships between the parameters of the leg trajectory and energy efficiency of the propulsion using a dynamics simulator. We find optimum parameter sets where optimization criterion is specific resistance. The results indicate that faster locomotion achieves higher energy efficiency. We then carry out hardware experiments and empirically derive the experimental specific resistance. We show that wheeled locomotion has an 8-times higher energy efficiency than the ordinary crawl gait. Finally, we compare the specific resistance of Roller-Walker with other walking robots described in the literature.

Park, Byungjae; Choi, Jinwoo; Chung, Wan Kyun

doi: 10.1163/156855312X633075pmid: N/A

Abstract This paper proposes a method to efficiently abstract the traversable regions of a bounded two-dimensional environment using the probabilistic roadmap (PRM) to plan the path for a mobile robot. The proposed method uses centroidal Voronoi tessellation to autonomously rearrange the positions of initially randomly generated nodes. The PRM using the rearranged nodes covers most of the traversable regions in the environment and regularly divides them. The rearranged roadmap reduces the search space of a graph search algorithm and helps to promptly answer arbitrary queries in the environment. The mobile robot path planner using the proposed rearranged roadmap was integrated with a local planner that considers the kinematic properties of a mobile robot, and the efficiency and the safety of the paths were verified by simulation.

Khaksar, Weria; Hong, Tang Sai; Khaksar, Mansoor; Motlagh, Omid Reza Esmaeili

doi: 10.1163/156855312X632166pmid: N/A

Abstract Path planning in unknown environments is one of the most challenging research areas in robotics. In this class of path planning, the robot acquires the information from its sensory system. Sampling-based path planning is one of the famous approaches with low memory and computational requirements that has been studied by many researchers during the past few decades. We propose a sampling-based algorithm for path planning in unknown environments using Tabu search. The Tabu search component of our method guides the sampling to find the samples in the most promising areas and makes the sampling procedure more intelligent. The simulation results show the efficient performance of the proposed approach in different types of environments. We also compare the performance of the algorithm with some of the well-known path planning approaches, including Bug1, Bug2, SRT, potential fields and the visibility graph. Furthermore, two different sampling strategies were used in the sampling procedure, including uniform and Gaussian distributions.