Differential-Difference Equations. By Richard Bellman and Kenneth L. Cooke. Pp. xvi, 465. 1963. (Academic Press)

A scheme is developed for classifying the types of motion perceived by a humanlike robot. It is assumed that the robot receives visual images of the scene using a perspective system model. Equations, theorems, concepts, clues, etc., relating the objects, their positions, and their motion to their images on the focal plane are presented. >

http://ieeexplore.ieee.org/iel2/815/3148/00100651.pdf

Robot vision

[서평]「The Unified Modeling Language User Guide」

Summary) The abstract should follow the structure of the article (relevance, degree of exploration of the problem, the goal, the main results, conclusion) and characterize the theoretical and practical significance of the study results. The abstract should not contain wording echoing the title, cumbersome grammatical structures and abbreviations. The text should be written in scientific style. The volume of abstracts (summaries) depends on the content of the article, but should not be less than 250 words. All abbreviations must be disclosed in the summary (in spite of the fact that they will be disclosed in the main text of the article), references to the numbers of publications from reference list should not be made. The sentences of the abstract should constitute an integral text, which can be made by use of the words “consequently”, “for example”, “as a result”. Avoid the use of unnecessary introductory phrases (eg, “the author of the article considers...”, “The article presents...” and so on.)

/pdf/ministry-of-education-and-science-of-the-russian-federation-7m2jn0xnm1.pdf

Ministry of Education and Science of the Russian Federation

Dynamic analysis of flexible manipulators, a literature review

Teaching a task to an industrial robotic manipulator can be done using either programming languages or “teaching by showing” techniques, where the operator drives the robot to prescribed positions using a teach pendant. An evolution of these techniques consists in the operator physically and safely interacting with the robot, by manually guiding its end-effector. Teaching of certain operations like spray painting is much more effective in this way. The present paper addresses this scenario, contributing with an exact formulation of the dynamics of the virtual tool, i.e. the tool whose dynamics the operator should feel when interacting with the robot. An admittance controller driven by the measurements of a force/torque sensor is designed in order to ensure that this virtual dynamic behavior is achieved. Experiments on an industrial robot are shown and discussed.

Assigning virtual tool dynamics to an industrial robot through an admittance controller

The features of modern collaborative robots, mainly their kinematic redundancy combined with the light-weight structure, can be fully exploited in parts assembly. Traditional robot-level paradigm to robot programming, that requires to explicitly specify the motion of the robot and allows to use contact forces for motion supervision only, cannot be easily applied to complex interaction tasks, such as robotic assembly. Instead, by shifting paradigm to skill-based programming, it is possible to specify force control actions at task level and inherently provide compliant capabilities, without the need to specify the motions of the robot. To this end, this paper presents a constraint-based programming framework for the implementation of assembly skills for light-weight redundant robots, enabling a reactive generation of motion trajectories based on force control requirements. The effectiveness of the proposed approach is experimentally validated on a bimanual assembly use case performed with the ABB YuMi dual-arm robot, requiring a peg-in-hole insertion and a cap-rotation task. Estimation of the interaction force/torque additionally enables the execution of the assembly operation without the need for exteroceptive sensors.

A constraint-based programming approach for robotic assembly skills implementation

The initial results of a research aimed at investigating to what extent high resolution encoders, which are getting available for common industrial motion control and robotics applications, can be exploited to compensate for non linear friction terms are presented in this paper. The 22 bits resolution sensor used allowed a neat analysis of the dynamic behavior of friction forces in the presliding regime, and especially of hysteresis loops. A recently proposed friction model has been validated. However, the influence of the cogging torque on the motor has been found to play a key role.

/pdf/friction-model-validation-in-sliding-and-presliding-regimes-3sgyv83vl7.pdf

Friction Model Validation in Sliding and Presliding Regimes with High Resolution Encoders

Describes the results of research on the oscillatory behavior that has been systematically experienced in the force measured during contact motion of an industrial robot. Two phenomena have been found to be mainly responsible for it, namely, the arm structural elasticity due to the torsional flexibility of the joints and the torque ripple of the brushless motors. The structural elasticity is characterized by a resonance frequency which varies with the arm configuration, while the torque ripple has harmonics of frequency proportional to the motor velocity. Most severe oscillations, and even loss of the contact, arise when the resonance and ripple frequency values come closer or match, so that elasticity and ripple excite each other.

Force oscillations in contact motion of industrial robots: an experimental investigation

PID control closed on the motor position is the most common solution in commercial servomechanisms. If significant compliance exists between the motor and load, performance limitations emerge if the load position behavior is properly considered. Quantification of the loss of performance at increasing nominal bandwidth of the closed loop system is the main result of this paper. After describing a simple procedure for identification of the relevant physical parameters, the performance is expressed as the H/sub /spl infin// norm of the transfer function from motor position setpoint to load position. A simple expression is given and experimentally assessed for this norm, in terms of inertial, elastic and damping parameters of the system, as well as of the nominal bandwidth of the closed loop system. Explicit formulas are finally given for load behavior concerned tuning of the PID controller.

Paolo Rocco

Papers

Assigning virtual tool dynamics to an industrial robot through an admittance controller

A constraint-based programming approach for robotic assembly skills implementation

Friction Model Validation in Sliding and Presliding Regimes with High Resolution Encoders

Force oscillations in contact motion of industrial robots: an experimental investigation

Load behavior concerned PID control for two-mass servo systems