48 research outputs found
Kinematic calibration of Orthoglide-type mechanisms from observation of parallel leg motions
The paper proposes a new calibration method for parallel manipulators that
allows efficient identification of the joint offsets using observations of the
manipulator leg parallelism with respect to the base surface. The method
employs a simple and low-cost measuring system, which evaluates deviation of
the leg location during motions that are assumed to preserve the leg
parallelism for the nominal values of the manipulator parameters. Using the
measured deviations, the developed algorithm estimates the joint offsets that
are treated as the most essential parameters to be identified. The validity of
the proposed calibration method and efficiency of the developed numerical
algorithms are confirmed by experimental results. The sensitivity of the
measurement methods and the calibration accuracy are also studied
Kinematic and stiffness analysis of the Orthoglide, a PKM with simple, regular workspace and homogeneous performances
International audienceThe Orthoglide is a Delta-type PKM dedicated to 3-axis rapid machining applications that was originally developed at IRCCyN in 2000-2001 to meet the advantages of both serial 3-axis machines (regular workspace and homogeneous performances) and parallel kinematic architectures (good dynamic performances and stiffness). This machine has three fixed parallel linear joints that are mounted orthogonally. The geometric parameters of the Orthoglide were defined as function of the size of a prescribed cubic Cartesian workspace that is free of singularities and internal collision. The interesting features of the Orthoglide are a regular Cartesian workspace shape, uniform performances in all directions and good compactness. In this paper, a new method is proposed to analyze the stiffness of overconstrained Delta-type manipulators, such as the Orthoglide. The Orthoglide is then benchmarked according to geometric, kinematic and stiffness criteria: workspace to footprint ratio, velocity and force transmission factors, sensitivity to geometric errors, torsional stiffness and translational stiffness
Kinematic calibration of orthoglide-type mechanisms
The paper proposes a novel calibration approach for the Orthoglide-type
mechanisms based on observations of the manipulator leg parallelism during
mo-tions between the prespecified test postures. It employs a low-cost
measuring system composed of standard comparator indicators attached to the
universal magnetic stands. They are sequentially used for measuring the
deviation of the relevant leg location while the manipulator moves the TCP
along the Cartesian axes. Using the measured differences, the developed
algorithm estimates the joint offsets that are treated as the most essential
parameters to be adjusted. The sensitivity of the meas-urement methods and the
calibration accuracy are also studied. Experimental re-sults are presented that
demonstrate validity of the proposed calibration techniqu
Stiffness modeling of non-perfect parallel manipulators
The paper focuses on the stiffness modeling of parallel manipulators composed
of non-perfect serial chains, whose geometrical parameters differ from the
nominal ones. In these manipulators, there usually exist essential internal
forces/torques that considerably affect the stiffness properties and also
change the end-effector location. These internal load-ings are caused by
elastic deformations of the manipulator ele-ments during assembling, while the
geometrical errors in the chains are compensated for by applying appropriate
forces. For this type of manipulators, a non-linear stiffness modeling
tech-nique is proposed that allows us to take into account inaccuracy in the
chains and to aggregate their stiffness models for the case of both small and
large deflections. Advantages of the developed technique and its ability to
compute and compensate for the compliance errors caused by different factors
are illustrated by an example that deals with parallel manipulators of the
Or-thoglide famil
Calibration of 3-d.o.f. Translational Parallel Manipulators Using Leg Observations
The paper proposes a novel approach for the geometrical model calibration of
quasi-isotropic parallel kinematic mechanisms of the Orthoglide family. It is
based on the observations of the manipulator leg parallelism during motions
between the specific test postures and employs a low-cost measuring system
composed of standard comparator indicators attached to the universal magnetic
stands. They are sequentially used for measuring the deviation of the relevant
leg location while the manipulator moves the TCP along the Cartesian axes.
Using the measured differences, the developed algorithm estimates the joint
offsets and the leg lengths that are treated as the most essential parameters.
Validity of the proposed calibration technique is confirmed by the experimental
results.Comment: ISBN: 978-3-902613-20-
A Six Degree-Of-Freedom Haptic Device Based On The Orthoglide And A Hybrid Agile Eye
This paper is devoted to the kinematic design of a new six degree-of-freedom
haptic device using two parallel mechanisms. The first one, called orthoglide,
provides the translation motions and the second one, called agile eye, produces
the rotational motions. These two motions are decoupled to simplify the direct
and inverse kinematics, as it is needed for real-time control. To reduce the
inertial load, the motors are fixed on the base and a transmission with two
universal joints is used to transmit the rotational motions from the base to
the end-effector. Two alternative wrists are proposed (i), the agile eye with
three degrees of freedom or (ii) a hybrid wrist made by the assembly of a
two-dof agile eye with a rotary motor. The last one is optimized to increase
its stiffness and to decrease the number of moving parts
Calibration of quasi-isotropic parallel kinematic Machines: Orthoglide
International audienceThe paper proposes a novel approach for the geometrical model calibration of quasi-isotropic parallel kinematic mechanisms of the Orthoglide family. It is based on the observations of the manipulator leg parallelism during motions between the specific test postures and employs a low-cost measuring system composed of standard comparator indicators attached to the universal magnetic stands. They are sequentially used for measuring the deviation of the relevant leg location while the manipulator moves the TCP along the Cartesian axes. Using the measured differences, the developed algorithm estimates the joint offsets and the leg lengths that are treated as the most essential parameters. Validity of the proposed calibration technique is confirmed by the experimental results