Modelling of surface roughness in inclined milling operations with circle-segment end mills

There is currently a lack of knowledge in the manufacturing of high complexity aerospace components. Impellers or blade-integrated disks (blisks) are expensive, and manufacturers tend to prefer reliability over productivity. Thus, manufacturing times are higher than they should be. These challenging parts need to be machined using new advanced tools for several reasons, such as requirement of 1) special and complex tool paths, 2) smoother cutting forces, and 3) good accessibility. Circle-segment or oval-form cutters have recently demonstrated their usefulness and adaptability in the machining of profile and free-form surface operations, and are becoming a solution for a wide range of applications and materials. However, machinists who use them know very little about such tools. In fact, there has been a lack of real-world modelling applications. This paper proposes for the first time a geometrical model that allows the prediction of the surface topography in flank-milling operations using circle-segment end mills. This time-domain model includes the most important mechanical and kinematical parameters during cutting: the tool geometry, feed rate, radial immersion, and tool runout. Tool orientation angles commonly used in 5-axis operations are also included. The developed model was positively verified against experimentally measured values in a milled wall made of aluminium Al7075T. This knowledge-based tool is useful for manufacturing companies and suppliers interested in optimizing and controlling their production parameters.     

Image processing system for industrial robots

The image data in a digitized picture can be represented by a set of edge lines and edge-point data. In the system described an object is recognized by comparing its parameters with those of various models. Criteria are given for declaring an object and model to be similar.     

Multiprocessor control system for industrial robots

This paper describes an advanced robot control system based on the three parallel processor boards. The controller has been designed as a general-purpose robot control system dedicated to controlling industrial robots with up to six degrees of freedom. The controller is based on a disk-oriented real-time operating system. The entire set of robot parameters can be monitored and changed by the user on-line. Source files, compilers, linkers and various utilities are provided as well.The main software layers include robot program interpreter, manipulator control facility, robot kinematics, dynamic feed-forward compensation, and digital servos. Basis, hand and joint coordinates are supported. Point-to-point and continuous path motions are provided. Digital and analog IO modules are included for synchronization with an environment. An acquisition system for monitoring and graphical presentation of robot coordinates, velocities and IO signals is provided. The paper ends with some experimental results for a six-degree of freedom robot.     

Optimal trajectory planning for industrial robots

An analysis of the results of an algorithm for optimal trajectory planning of robot manipulators is described in this paper. The objective function to be minimized is a weighted sum of the integral squared jerk and the execution time. Two possible primitives for building the trajectory are considered: cubic splines or fifth-order B-splines. The proposed technique allows to set constraints on the robot motion, expressed as upper bounds on the absolute values of velocity, acceleration and jerk. The described method is then applied to a 6-d.o.f. robot (a Cartesian gantry manipulator with a spherical wrist); the results obtained using the two different primitives are presented and discussed.     

A path planning algorithm for industrial robots

Instead of using the tedious process of robot teaching, an off-line path planning algorithm has been developed for industrial robots to improve their accuracy and efficiency. Collision avoidance is the primary concept to achieve such goal. By use of the distance maps, the inspection of obstacle collision is completed and transformed to the configuration space in terms of the robot joint angles. On this configuration map, the relation between the obstacles and the robot arms is obvious. By checking the interference conditions, the collision points are indicated with marks and collected into the database. The path planning is obtained based on the assigned marked number of the passable region via wave expansion method. Depth-first search method is another approach to obtain minimum sequences to pass through. The proposed algorithm is experimented on a 6-DOF industrial robot. From the simulation results, not only the algorithm can achieve the goal of collision avoidance, but also save the manipulation steps.     

Base frame calibration for coordinated industrial robots

To solve the problem of base frame calibration for coordinated multi-robot system, a new method is proposed in this paper. It is carried out through a series of “handclasp” manipulations between two coordinated robots, then a preliminary result can be reached by the calibrating equation. After that, in order to make sure that the calibrated rotation matrix is orthonormal, an optimal estimation of the relative rotation between the base frames of coordinated manipulators is solved out under the criterion of optimal Frobenius norm approximation. By the quaternion representation for rotation matrix and the Lagrange Multiplier method, an orthonormal matrix can be reached which is just the unknown calibrating result for base frames of the coordinated robots. Simulation and experiment results have verified the validity and effectiveness of the proposed method.     

Holographic measurement of industrial robots

Application and/or user's demand on industrial robot performance is increasing rapidly. Higher positioning accuracy, payload capability, speed, larger working area, etc. are required, mostly depending on the application. Demand will be even higher in the future.In some manufacturing system application, e.g. material handling and assembly, the positioning accuracy of industrial robots is sometimes not adequate. At the same time, in the latter case, higher speeds are desired. As the case is similar in many areas, utilization of robots to perform manufacturing operations is accelerating each day. Therefore, higher performance characteristics are desired.To increase the positioning accuracy of robots, factors degrading accuracy must be detected and, if possible, eliminated or minimized. In this paper load-induced inaccuracy for an industrial robot is investigated and a compensation algorithm for the deflection is derived to improve the positioning accuracy.     

Impedance control of industrial robots

Manipulation fundamentally requires the manipulator to be mechanically coupled to the object being manipulated. A consideration of the physical constraints imposed by dynamic interaction shows that control of a vector quantity such as position or force is inadequate and that control of the manipulator impedance is necessary. Techniques for planning and control of manipulator behavior are presented which result in a unified approach to target acquisition, obstable avoidance, kinematically constrained motion, and dynamic interaction. A feedback control algorithm for implementing a cartesian end-point impedance on a nonlinear manipulator is presented. The modulation of end-point impedance independent of feedback is also considered. A method for choosing the impedance appropriate to a task using optimization theory is discussed.     

Variable structure model following control for industrial robots

A variable structure model following control (VSMFC) strategy for the control of most types of industrial robots (according to a classification ofCoiffet 1983) has been presented. For 99% of the robots given in the classification of Coiffet (1983), the dynamics of each link can be represented by a simple model with the nonlinearities and coupling dynamics decoupled from the linear part (Stoten 1985). This facilitates the designer to have a modified VSMFC law, which will maintain sliding mode motion of the error and its derivative, referred to as the representative point (RP), on a user chosen switching line and to drive the RP to the origin of the error plane (error is defined as the difference between the states of the reference model and those of the plant). When in sliding mode the system remains insensitive to parameter variations and disturbances     

Dynamic NC simulation of milling operations

To increase productivity in manufacturing, accurate cutting-simulation systems have increasingly been used to study the performance of machining processes. A new dynamic cutting-simulation system that can simulate the dynamic behaviour of the milling cutting force along the programmed NC toolpath is presented in the paper. The radial and axial depths of cut in the cutting process are extracted from a geometric cutting-simulation system on a workstation. Then, the radial and axial depths of cut and the other given cutting parameters are transmitted to a mechanistic model of the milling process from which the dynamic cutting force is obtained. There is good agreement between the simulated and measured cutting forces.     

Expected innovation in industrial robots

The market of industrial robots has been growing these years. The shipping amount attained in 2014 was over 230,000 units in the world, and better result was achieved in 2015. There have been great changes in more than 30 years of history of industrial robot market. The market has been expanding from limited countries to worldwide and from limited industries to various applications. However, the scale of the robot market is still small compared to the remarkable growth of the manufacturing market in the world. Innovations are required in the system integration, materials, and elemental technologies for wider deployment and usage of industrial robots. The innovation in system integration has a goal to provide customers with the best fit and reasonably priced solutions for the problems in manufacturing processes, as well as to balance the profit for system integrators. The innovation in material and elemental technologies has a goal to solve the problems that still remain in robot technologies since the beginning of the market. Higher reliability and better cost performance should be established for the advanced applications in the future. The collaborations of various industries are also required to achieve the innovations.     

Feedrate planning for machining with industrial six-axis robots

Nowadays, the adaptation of industrial robots to carry out high-speed machining operations is strongly required by the manufacturing industry. This new technology machining process demands the improvement of the overall performances of robots to achieve an accuracy level close to that realized by machine-tools. This paper presents a method of trajectory planning adapted for continuous machining by robot. The methodology used is based on a parametric interpolation of the geometry in the operational space. FIR filters properties are exploited to generate the tool feedrate with limited jerk. This planning method is validated experimentally on an industrial robot.     

Recent progress on programming methods for industrial robots

Although an automated flexible production cell is an intriguing prospect for small to median enterprises (SMEs) in current global market conditions, the complexity of programming remains one of the major hurdles preventing automation using industrial robots for SMEs. This paper provides a comprehensive review of the recent research progresses on the programming methods for industrial robots, including online programming, offline programming (OLP), and programming using Augmented Reality (AR). With the development of more powerful 3D CAD/PLM software, computer vision, sensor technology, etc. new programming methods suitable for SMEs are expected to grow in years to come.     

Model reference adaptive control algorithms for industrial robots

In this paper some problems concerning the control of multifunctional manipulators (industrial robots) with high speed continuous movements are investigated. Although deterministic approaches to the control of robots, whose model are highly interconnected and non-linear, are known alternative approaches based on the Model Reference Adaptive System (MRAS) method of control are possible and useful. In the paper it is proved that a generalized MRAS control assures the convergence to a suitable reference model for a class of processes: the manipulator is shown to belong to such a class. The paper is completed by some applications evaluated by simulation.     

Feedforward dynamics for the control of articulated multi-limb robots

We describe a general approach for using linearizing feedforward control inputs for large degree of freedom (dof) multi-limb robots operating in scenarios involving motion and force constraints, and under-actuated degrees of freedom arising from the task and the environment. Our solution is general and has low computational cost needed for real-time control loops. It supports the tuning of the feedforward term to meet multiple task objectives. Being structure-based, it is able to easily accommodate changes in motion and force constraints that often occur in robotics scenarios.     

Development of CAD codes for the job integration of industrial robots

The work of the Industrial Robot Design Research Group working at the University of Genoa, Italy, is summarized. The reasons for developing special-purpose CAD codes are noted, together with a discussion of the approach that has been utilized. An example procedure concerning the selection of the controlling strategies is presented, with typical output results. The integration of the robotic devices into manufacturing lines is discussed with an indication of the computational codes presently under development.