Francisco J Campa

• Associate Professor. Department of Mechanical Engineering. University of the Basque Country UPV/EHU
• Professor (Associate) at University of the Basque Country

In the present work, a parallel continuum manipulator for trunk rehabilitation tasks for patients who have suffered a stroke was analyzed and redesigned. The manipulator had to perform active assistance exercises for the motor recovery of the patient. Based on this background, a series of requirements were defined, which determined the design frame...

This paper presents a novel parallel manipulator capable of generating two translations (2T), inside a vertical plane, and two rotations (2R), about horizontal axes, which are required in aerospace, manufacturing and rehabilitation fields. These four degrees of freedom are reached by means of a unique RRU and three RSS kinematic chains connected to...

Gait and balance have a direct impact on patients’ independence and quality of life. Due to a higher life expectancy, the number of patients suffering neurological disorders has increased exponentially, with gait and balance impairments being the main side effects. In this context, the use of rehabilitation robotic devices arises as an effective an...

In this study, the novel mobile dynamometric platform, OREKA, was utilized to perform an extensive analysis of the centre of pressure behaviour during different tilt motion exercises. This platform is based on a parallel manipulator mechanism and can perform rotations around both horizontal axes and a vertical translation. A group of participants t...

This paper presents a synthesis method that leads to a novel family of 4-degrees of freedom (DOF) parallel manipulators (PM) capable of generating the two translations and two rotations (2T2R) required for balance rehabilitation, namely, two translations inside the sagittal plane and antero-posterior and medio-lateral rotations. The proposed synthe...

The measurement of the Center of Pressure (COP) of a patient on a dynamometric platform is one of the most recognized methods for evaluating patient balance during rehabilitation. In this work, the influence of an asymmetric platform design on the measurement of COP in static conditions has been analyzed for a rehabilitation machine with a mobile d...

In this paper, a novel parallel platform for balance testing called OREKA is used to analyze the Centre of Pressure movement of several subjects during tilting motions. The platform, based on the 3PRS architecture, is capable of rotations around both horizontal axes and a vertical translation. Several subjects have performed different exercises to...

One of the first rehabilitation exercises in a hemiplegic patient is the recovery of the trunk balance, as a previous stage for the gait training. In this paper, a solution to assist this task with a robotic device is proposed and discussed. It is based on a compliant parallel kinematics manipulator of 4 degrees of freedom, 3 rotations and a transl...

Compliant mechanisms are widely used for instrumentation and measuring devices for their precision and high bandwidth. In this paper, the mechatronic model of a compliant 3PRS parallel manipulator is developed, integrating the inverse and direct kinematics, the inverse dynamic problem of the manipulator and the dynamics of the actuators and the con...

The objective of the present work is to improve a device for rehabilitating the trunk balance and motion of patients who have suffered a stroke. The device is based on a parallel continuum manipulator coupled to a standing frame, where a wearable jacket is actuated by four flexible limbs connected to rotary motors. It has been designed to perform b...

The objective of the present work is to develop a device for training the trunk balance and motion during the early stage of rehabilitation of patients who have suffered a stroke. It is coupled to a standing frame and is based on a parallel continuum manipulator where a wearable jacket is moved by four flexible limbs actuated by rotary motors, achi...

Parallel Continuum Mechanisms are closed-loop mechanical systems formed by flexible rods connected to a rigid end-effector and actuated from the base attachments of such rods. It was shown in previous works that they have analogous kinematic features to rigid-link parallel mechanisms. Position analysis is a force equilibrium problem with a multipli...

The consequence of the population aging in last decades has been an increase of age-related disorders, such as multiple sclerosis, Parkinson’s disease, spinal cord injury or central nervous diseases, causing a deficiency in mobility and thus affecting the quality of life of adults [1, 2].

A common problem in motion control is the onset of vibrations due to the inertial forces when a compliant load is being displaced. It is the case of the vibration of large machine tools, but also the vibration of slender loads in pick&place. The main goal of the present work is to predict and minimise the overshoot that a compliant load moved by a...

One of the main advantages of parallel manipulators over serial manipulators is their capacity to achieve faster and more precise movements, which is why they are used in many industrial applications. A parallel manipulator is formed by two or more parallel sets of rigid elements connected in series, and the corresponding actuators. Nevertheless, a...

Parallel continuum mechanisms are closed, kinematic, chained compliant mechanisms that are mobile due to flexible and slender elements. Large deformations and the force-moment equilibrium require a more complex modeling of the kinematic analysis than in their rigid-link counterparts. Although real-time solutions to the position problem using numeri...

Parallel Continuum Mechanisms are manipulators whose end-effector is connected with several compliant legs. Continuum manipulators of such kind have been considered historically serial devices because most of them have a long slender form. Nevertheless, these architectures contain aspects resembling their rigid-link parallel analogs. In this paper,...

Parallel Continuum Manipulators are parallel mechanisms which movement is due to the deformation of some of their elements, usually flexible rods. Provided that rods are straight in their stress-free reference state and that the movement of the mechanism is within a plane, elliptic integral solution can be used in order to get the deformation of ea...

The aim of this work is to develop a mechatronic model for servodrives that move a compliant load, which is the case of large heavy machine tools. The model integrates the dynamics of the motor, transmission chain and compliant load as well as the dynamics of the control and is used to calculate the maximum overshoot in the load when it reaches the...

It is important for the mechatronic design of robotic systems to rely on accurate models. To that end, system identification methods are a convenient tool to obtain the values of the unknown dynamic parameters which play a key role. In this paper, it is investigated the application of the principle of energy equivalence to easily obtain a suitable...

In the field of parallel kinematics few designs use highly deformable elements to obtain the end effector movement. Most compliant mechanisms rely on notches or shape changes to simulate a standard kinematic joint. In this work a kinematic model of a simple parallel continuum mechanism that combines a deformable element and cable is presented. The...

High-performance position control in machine tools can only be achieved modeling the dynamic behavior of the mechatronic system composed by the motor, transmission and control during the design stage. In this work, a complex analytical model of a ball screw drive is presented and integrated in a mechatronic model of the actuator to predict the dyna...

The objective of this work is to develop a manipulator of 5 degrees of freedom for micromilling. It consists of a XY stage under a 3PRS compliant parallel mechanism, obtaining the advantages of the compliant joints as are higher repetitiveness, smoother motion and a higher bandwidth, due to the high precision demanded from the process, under 0.1 μm...

The development of large machinery in the industry of the machine tool implies moving heavy structural components and pieces. The consequence is the apparition of inaccuracies at the tool tip during the motion due to the high inertial forces acting on the compliant machine. To predict the dynamic behavior of these machines, a three degree of freedo...

Current CAM and milling verification software packages are not ready to predict form and surface errors derived from non-ideal conditions such as runout tool error or tool–workpiece flexibility. As a consequence, high-end parts like integral blade rotors (IBR) suffer from this lack of estimation to achieve a sound manufacturing process preparation....

Abstract In this paper, a procedure for the kinematic design of a 3-PRS compliant parallel manipulator of 3 degree of freedom is proposed. First, under the assumption of small displacements, the solid body kinematics of the 3-PRS has been studied, performing a comprehensive analysis of the inverse and forward kinematic problem, and calculating the...

In this work a mechatronic model was developed for a parallel Multi-Axial Simulation Table (MAST) mechanism. The dynamics of the mechanism was obtained using the principle of energy equivalence and Boltzmann–Hamel equations. In this way, the procedure to obtain the explicit dynamic equations is simplified and has the advantage of being systematic....

In this paper, the interaction between the dynamics of the routing process and the vibration behavior of the ARABA I lightweight machine is presented. Firstly, the dynamics of the routing is evaluated by the critical depth of cut of the lobes diagrams of the process. Secondly, the structural dynamics of the machine is analyzed by means of its exper...

In this paper, authors show the results of performance simulation of a 3PRS lower-mobility parallel manipulator actuated by electronic devices. The simulation includes a mechatronic model of the actuators, the dynamic response of the mechanism found using the Boltzmann-Hamel equations, and a model of the control. The dynamics of the actuators is mo...

The present work deals with the development of a hybrid manipulator of 5 degrees of freedom for milling moulds for microlenses. The manipulator is based on a XY stage under a 3PRS compliant parallel mechanism. The mechanism takes advantage of the compliant joints to achieve higher repetitiveness, smoother motion and a higher bandwidth, due to the h...

Explicit Dynamic equations are needed for simulation and control in the field of Mechatronics. Several classical methods are available to get Dynamic equations. Regarding those methods that aim exclusively at the equations relating applied torques and motion generated, i.e. avoiding any calculus of joint wrenches, Analytical mechanics offers severa...

Productivity and surface finish are typical user manufacturer requirements that are restrained by chatter vibrations sooner or later in every machining operation. Thus, manufacturers are interested in knowing, before building the machine, the dynamic behaviour of each machine structure with respect to another. Stability lobe graphs are the most rel...

In this paper, a mechatronic model of a planar parallel manipulator is developed and experimentally validated. The model considers the dynamics of the actuators, as well as the PID control algorithm with position, velocity and current cascaded loops and their timing. As our main contributions, the dynamics of the manipulator have been solved using...

Flexure stages are widely used in the field of micro and nanopositioning because of their repeatability and precision, which is due to the lack of joints that induces uncertainty. In the present Twork, a XY flexure stage has been analyzed and redesigned to reduce the axis cross-coupling, which is due to a parasitic motion in the amplification stage...

The application of laser cladding technology is becoming widely extended in the industrial environment due to its advantages of high added value and direct manufacturing or repair of complex parts. These complex parts require 5-axis laser cladding deposition processes whose programming demands optimized and continuous tool paths. The present work d...

The aim of this work is to approach the difficulties students usually encounter when facing up to kinematic analysis of mechanisms. A deep understanding of the kinematic analysis is necessary to go a step further into design and synthesis of mechanisms. We can conclude from experience that supporting and complementing the theoretical lectures with...

The stability of a thin wall workpiece milling process is investigated through a single degree of freedom system that mimics the milling machine operation. The stability lobes were computed by using the Enhanced Multistage Homotopy Perturbation Method (EMHPM), the Chebyshev Collocation, the Semi-Discretization and Full-Discretization methods. A com...

The aim of the present work is to present a fast identification method to estimate the inertial and friction parameters of a rigid body dynamic model of an electromechanical actuator. These are the dominant effects that determine the dynamics of machines and although the inertia is easily predictable, the friction can only be accurately known perfo...

Aeronautics is a business in a continuous growing sector and aircraft manufacturing is without any doubt a high-priced process. Each part of the aircraft and particularly engine parts represent the most expensive elements due to the difficulty of manufacturing their complex geometry. In this case, the test piece to carry out the study has been the...

Nowadays, aluminum manufacturing companies are required to improve the manufacturing process of components with complex geometric details. This improvement requires an optimization of the process, resulting on higher cutting parameters. In thin floor parts, being low rigidity structures, the increase of cutting parameters brings as a conclusion the...

In this work, a methodology for the assessment of the geometrical accuracy of a multiaxis machine, the type usually called multitasking machine, was fully developed. For this purpose, the well-known formulation by Denavit and Hartenberg was applied. Multitasking machines are derived from lathes in which turrets are substituted by milling spindles,...

The objective of the vibration assisted machining techniques is to improve the traditional cutting processes by the application of an external vibration to the cutting edge to achieve improvement in the chip removal mechanism and in the manufactured part quality. Currently, two techniques are most common for vibration-assisted machining due to thei...

A comparative study of the dynamics of the 3-PRS parallel mechanism between the full case, considering the parasitic motions, and a simplified one, ignoring the parasitic motions, is presented in this work. A simplified dynamic model would be of great interest to determine the dimensions of the actuators and to solve the dynamic problem much easier...

This paper deals with the static characterisation of a parallel manipulator for routing processes. Since accuracy and surface finishing are critical in all machining processes, the performance of a parallel machine is analysed in this paper in terms of these parameters. Using a previously developed static analysis methodology, the stiffness of the...

This work deals with the characterization of a three stage multivariable tool used for high-performance milling and the modelling of its dynamic behaviour to predict the stability against chatter. The influence of the variable pitch, variable helix and variable rake angle on each cutting edge of the tool is modeled to calculate the stability lobes...

Modern industry requires high-precision machines and processes. This requirement implies the determination and reduction of all possible sources of error. For turning, a main error is related to machine–tool–workpiece deformation caused by cutting force. On the other hand, current turning centers are structurally more complicated than conventional...

Boring operations of deep holes with a slender boring bar are often hindered by the precision because of their low static stiffness and high deformations. Because of that, it is not possible to remove much larger depths of cuts than the nose radius of the tool, unlike the case of turning and face milling operations, and consequently, the relationsh...

Boring operations of deep holes with a slender boring bar are often hindered by the precision because of their low static stiffness and high deformations. Because of that, it is not possible to remove much larger depths of cuts than the nose radius of the tool, unlike the case of turning and face milling operations, and consequently, the relationsh...

Chatter vibrations produced during turning of slender parts or boring with flexible tools lead to a wavy work surface, and reduce the spindle headstock life span as well. This study deals with the problem of chatter prediction in straight turning of non-rigid parts, making use of round inserts. A stability model for straight turning has been develo...

In this paper, a study of the capabilities of a parallel manipulator with four degrees of freedom for machining application is presented. Specifically, routing tasks will be considered. To carry out this study, a process model that allows the dynamic behaviour of robot based on the phenomenon of chatter to be considered is used. The model takes int...

In this chapter the main methods, machining strategies and possible problems when flank milling complex surfaces, are deeply explained. Flank milling is an operation defined by using large axial depth of cut with end milling tools, high cutting speed and relatively small radial depths of cut. This process is especially recommended for ruled surface...

This chapter deals with the basic definitions and parameters of the milling operation, currently the most important of the chip removal techniques due to its versatility in manufacturing complex and precise geometries. In this chapter, the basic aspects of tool and machining operations are presented, along with the basic cutting parameters to defin...

High-speed machining has improved performance in manufacturing sectors such as the aeronautical, automotive, and mould and die industries. However, one problem of reaching such high speeds is the self-excitation of the spindle-tool system during the machining process. This so-called chatter vibration produces several negative effects: a reduction i...

Ever increasingly, universities have to face the demands of their students regarding tools and methods to complete their education in preparation for the industrial environment. On the other hand, the university has to meet a Research and Development function oriented to the improvement of the competitiveness of that environment. These are two diff...

This paper provides an integrated approach for designing large milling machines, taking both mass reduction of mobile structural components and the maximum material removal rate into account. This approach considers a representative milling operation and a productivity target as a starting point, and then deals with the design of the machine to ach...

Ever increasingly, universities have to face the demands of their students regarding tools and methods to complete their education in preparation for the industrial environment. on the other hand, the university has to meet a Research and Development function oriented to the improvement of the competitiveness of that environment. These are two diff...

This book presents an integrated 'machine and process' approach that is based on stability lobe diagrams for designing large-volume milling machines bearing in mind their productivity, reliability and accuracy as well as their eco-efficiency. In fact, eco-efficiency of machining processes is an issue of increasing concern among both machine tool bu...

A common problem in the aeronautical industry is the chatter vibration due to the lack of dynamic stiffness in the milling of thin walls and thin floors. The present work proposes a method for chatter avoidance in the milling of flexible thin floors with a bull nose end mill. It allows the calculation of the thickness previous to finish milling or...

The milling of thin parts is a high added value operation where the machinist has to face the chatter problem. The study of the stability of these operations is a complex task due to the changing modal parameters as the part loses mass during the machining and the complex shape of the tools that are used. The present work proposes a methodology for...

The present work presents the results obtained when an ultrasonic vibration is applied to tool on the turning of mild steels. Currently high‐end materials, usually present low machinability so it is necessary to employ new machining technologies. Ultrasonic assisted turning (UAT) is presented as an effective process for machining these difficult‐to...

Machining processes are frequently faced with the challenge of achieving more and more precision and surface qualities. These requirements are usually attained taking into account some process variables, including the cutting parameters and the use or not of refrigerant, leaving aside the mechanical aspects associated with the infl uence of machine...

In this work, the advantages and drawbacks of Ultrasonic Assisted Turning (UAT) have been investigated focusing on the effect of tool vibration on surface quality. Several experiments have been performed on mild steels changing the cutting speed, feed and depth of cut, to study how the influence of the ultrasonic vibration on the surface roughness...

Chatter is the most classical problem in machining. It is prone to occur in low rigidity structures generating poor surface quality and harmful vibrations which could damage any part of the machine-tool system. In finishing operations, the effect of the tool nose radius should be taken into account in order to obtain safe and reliable cutting condi...

Machinery manufacturers are facing the challenge of designing machine tools that are productive, accurate and reliable and that at the same time consume the least possible amount of material and energy resources. In view of this, this paper presents a multidisciplinary methodology for designing milling machines that achieve a high level of producti...

This paper presents a model for the prediction of surface topography in peripheral milling operations taking into account that the tool vibrates during the cutting process. The model includes the effect of tool vibrations in the equations of the cutting edge paths, which are transformed into equivalent polynomial equations and solved for discrete p...

This article deals with the new development of a family of router milling tools for the high-performance milling of carbon fiber reinforced plastics. The new milling tools are shaped by multiple left-hand and right-hand helical edges, which form small pyramidal edges along the cutting length. Several substrates and coatings have been tested includi...

This chapter deals with spindle technologies for machine tools. The machine tool spindle provides the relative motion between the cutting tool and the workpiece which is necessary to perform a material removal operation. In turning, it is the physical link between the machine tool structure and the workpiece, while in processes like milling, drilli...

This chapter is focused on analysing new concepts and trends related to the structure of machine tools. In fact, the structure of the machine has a decisive influence on the three main parameters that define the capabilities of a machine, which are: motion accuracy, the productivity of the machine and the quality of machining. In this respect, this...

This paper presents a model for the topography prediction of ball-end milled surfaces, considering the tool parallel axis offset. First, the equations of cutting edge trajectories and the envelope equation of the material swept by the tool are derived. Later, the trajectories are cut by planes perpendicular to the feed direction obtaining a set of...

El presente artículo presenta una nueva metodología para reducir el tiempo de mecanizado de la fase de acabado de los troqueles que han surgido para conformar los nuevos materiales conocidos como Aceros Avanzados de Alta Resistencia, actuando en dos ejes operativos. Por un lado se trata de minimizar el error de flexión en el mecanizado de estampas...

The milling of thin-walled parts can become a seriously complex problem because the parts have variable dynamics. Firstly, the dynamics evolution of the part has been calculated through Finite Element Method (FEM) analysis. Then, the 3D stability lobes have been calculated for the thin walls and the thin floor. Finally, several milling tests have b...

The main drawback of the high speed milling of monolithic parts for the aerospace industry is the high buy-to-fly ratio that leads to a huge material waste. This problem is caused by the need to stiffen the part during the machining in order to avoid chatter, excessive vibration and residual stresses. The present work proposes a methodology for the...

In this paper, a three-dimensional dynamic model for the calculation of the stability lobes of low rigidity parts is applied for the prediction of chatter vibrations during the finish milling of aeronautical parts that include thin walls and thin floors. Hence, an accurate selection of both axial depth of cut and spindle speed can be done. The foll...

In this paper, a 3D dynamic model for the prediction of the stability lobes of high speed milling is presented, considering the combined flexibility of both tool and workpiece. The main aim is to avoid chatter vibrations on the finish milling of aeronautical parts, which include thin walls and thin floors. In this way the use of complex fixtures is...

High speed machining of low rigidity structures is a widely used process in the aeronautical industry. Along the machining of this type of structures, the so-called monolithic components, large quantities of material are removed using high removal rate conditions, with the risk of the instability of the process. Very thin walls will also be milled,...

At present, airframes are mainly composed of monolithic components, instead of small parts joined using welding or riveting. Ribs, stringers, spars, and bulkheads can be included in this category. After milling, they are assembled and joined to the aircraft skins, which have also been milled. The aim of these parts is to obtain a good strength-weig...

In this paper, a three-dimensional dynamic model for the prediction of the stability lobes of high speed milling is presented considering the combined flexibility of both tool and workpiece. The aim is to avoid chatter vibrations in the finish milling of aeronautical parts that include thin walls and thin floors, taking into account the variation o...

The milling of thin-walled parts can become a seriously complex problem. In this work, the problem of the variable dynamics of a test part has been solved through the calculation of 3D stability lobes which add a third dimension with the tool position along the part, to the traditional depth of cut-spindle speed pair. First, the dynamics of a test...

The milling of thin-walled parts can become a seriously complex problem because the parts have variable dynamics. Firstly, the dynamics evolution of the part has been calculated through Finite Element Method (FEM) analysis. Then, the 3D stability lobes have been calculated for the thin walls and the thin floor. Finally, several milling tests have b...

In this work a mechanistic model for peripheral milling is presented, taking into account the flexibility of slender end mills. The contribution of this paper is the obtention of the real tool center displacements and the real cutting forces, since the model takes into account the instantaneous force balance between the cutting forces and the elast...

1 Universidad del País Vasco, UPV/EHU: fran.campa@ehu.es 2 Fundación FATRONIK. 3 École Nationale d'Ingénieurs de Tarbes. RESUMEN Este trabajo trata de la aplicación de un modelo de estabilidad tridimensional para el cálculo de diagramas de lóbulos para el mecanizado de piezas de rigidez reducida, paredes y suelos delgados, típicas de la industria a...

Nowadays, difficult to cut materials such as nickel and titanium alloys are used more and more frequently because of their excellent behavior even at high temperatures. From this point of view, it is clear the interest of the aeronautical industry in these materials. This paper explores the complex force relationship between the work-piece and the...