Positional capability of a hexapod robot for machining applications

Barnfather, J. D.; Goodfellow, Martin J.; Abram, T.J.

doi:10.1007/s00170-016-9051-0

Cited by 13 publications

(7 citation statements)

References 37 publications

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“…The equation of the dynamic model of the robot used for simulations is equation (1). The nonzero elements of the matrix MðrÞ 2 R 9Â9 are 29 The nonzero elements of the matrix Cðr; _ rÞ 2 R 9Â9 are…”

Section: Kinematic Structure Of the Parallel 3-rrr Robotmentioning

confidence: 99%

A stable proportional–proportional integral tracking controller with self-organizing fuzzy-tuned gains for parallel robots

Salas

Orrante-Sakanassi

Juárez

et al. 2019

International Journal of Advanced Robotic Systems

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Parallel robots are nowadays used in many high-precision tasks. The dynamics of parallel robots is naturally more complex than the dynamics of serial robots, due to their kinematic structure composed by closed chains. In addition, their current high-precision applications demand the innovation of more effective and robust motion controllers. This has motivated researchers to propose novel and more robust controllers that can perform the motion control tasks of these manipulators. In this article, a two-loop proportional–proportional integral controller for trajectory tracking control of parallel robots is proposed. In the proposed scheme, the gains of the proportional integral control loop are constant, while the gains of the proportional control loop are online tuned by a novel self-organizing fuzzy algorithm. This algorithm generates a performance index of the overall controller based on the past and the current tracking error. Such a performance index is then used to modify some parameters of fuzzy membership functions, which are part of a fuzzy inference engine. This fuzzy engine receives, in turn, the tracking error as input and produces an increment (positive or negative) to the current gain. The stability analysis of the closed-loop system of the proposed controller applied to the model of a parallel manipulator is carried on, which results in the uniform ultimate boundedness of the solutions of the closed-loop system. Moreover, the stability analysis developed for proportional–proportional integral variable gains schemes is valid not only when using a self-organizing fuzzy algorithm for gain-tuning but also with other gain-tuning algorithms, only providing that the produced gains meet the criterion for boundedness of the solutions. Furthermore, the superior performance of the proposed controller is validated by numerical simulations of its application to the model of a planar three-degree-of-freedom parallel robot. The results of numerical simulations of a proportional integral derivative controller and a fuzzy-tuned proportional derivative controller applied to the model of the robot are also obtained for comparison purposes.

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Section: Kinematic Structure Of the Parallel 3-rrr Robotmentioning

confidence: 99%

A stable proportional–proportional integral tracking controller with self-organizing fuzzy-tuned gains for parallel robots

Salas

Orrante-Sakanassi

Juárez

et al. 2019

International Journal of Advanced Robotic Systems

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show abstract

“…Variance over the working envelope is supported as being feasible in the initial literature review and prior experimental work done to quantify positional error [69] and to measure deflection and dynamic stiffness for cutting parameter selection [40][41][42]. The excessive presence of outliers casts doubt over validity of remaining data from these cylinders so they are eliminated entirely.…”

Section: Cylindrical Pocket Machining Trialsmentioning

confidence: 99%

Achievable tolerances in robotic feature machining operations using a low-cost hexapod

Barnfather

Goodfellow

Abram

2017

Int J Adv Manuf Technol

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Portable robotic machine tools potentially allow feature machining processes to be brought to large parts in various industries, creating an opportunity for capital expenditure and operating cost reduction. However, robots lack the machining capability of conventional equipment, which ultimately results in dimensional errors in parts. This work showcases a low-cost hexapod-based robotic machine tool and presents experimental research conducted to investigate how the widely researched robotic machining challenges, e.g. structural dynamics and kinematics, translate to achievable tolerance ranges in real-world production to highlight currently feasible applications and provide a context for considering technology improvements. Machining trials assess the total dimensional errors in the final part over multiple geometries. A key finding is error variation which is in the sub-millimetre range, although, in some cases, upper tolerance limits < 100 μm are achieved. Practical challenges are also noted. Most significantly, it is demonstrated that dimensional machining error is mainly systematic in nature and therefore that the total error can be dramatically reduced with in situ measurement and compensation. Potential is therefore found to achieve a flexible, highperformance robotic machining capability despite complex and diverse underlying scientific challenges. Overall, the work presented highlights achievable tolerances in lowcost robotic machining and opportunities for improvement, also providing a practical benchmark useful for process selection.

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“…Similar to the wellknown Sprint Z3 head, a 3-degree of freedom (3-DOF) PKM module called the A3 head has been designed for large structural component machining [18]. Moreover, the dynamics and positional capability of the Fanuc F200iB hexapod robot have been investigated for mobile machining [19,20]. Another portable large-volume machine tool solution is the hybrid serial-parallel mechanism.…”

Section: Introductionmentioning

confidence: 99%

A novel six-legged walking machine tool for in-situ operations

Liu¹,

Tian²,

Gao³

2020

Front. Mech. Eng.

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The manufacture and maintenance of large parts in ships, trains, aircrafts, and so on create an increasing demand for mobile machine tools to perform in-situ operations. However, few mobile robots can accommodate the complex environment of industrial plants while performing machining tasks. This study proposes a novel six-legged walking machine tool consisting of a legged mobile robot and a portable parallel kinematic machine tool. The kinematic model of the entire system is presented, and the workspace of different components, including a leg, the body, and the head, is analyzed. A hierarchical motion planning scheme is proposed to take advantage of the large workspace of the legged mobile platform and the high precision of the parallel machine tool. The repeatability of the head motion, body motion, and walking distance is evaluated through experiments, which is 0.11, 1.0, and 3.4 mm, respectively. Finally, an application scenario is shown in which the walking machine tool steps successfully over a 250 mm-high obstacle and drills a hole in an aluminum plate. The experiments prove the rationality of the hierarchical motion planning scheme and demonstrate the extensive potential of the walking machine tool for in-situ operations on large parts.

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Positional capability of a hexapod robot for machining applications

Cited by 13 publications

References 37 publications

A stable proportional–proportional integral tracking controller with self-organizing fuzzy-tuned gains for parallel robots

A stable proportional–proportional integral tracking controller with self-organizing fuzzy-tuned gains for parallel robots

Achievable tolerances in robotic feature machining operations using a low-cost hexapod

A novel six-legged walking machine tool for in-situ operations

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