Kinematics of a 6-DOF parallel manipulator with two limbs actuated by spherical motion generators

Inspired by dual-arm-like manipulation, a novel 6-DOF parallel manipulator with two spherical-universal-revolute limbs is proposed. Compared with general 6-DOF parallel manipulators with six limbs, this new manipulator actuated by spherical motion generators has only two limbs, which brings advantages such as fewer active limbs for avoiding interference, larger reachable and orientational workspace for complex operating, more actuators integrated in active modules for decreasing installation errors and increasing compactness. In this paper, the kinematics of this novel parallel manipulator is solved and illustrated, covering its inverse and forward position analysis, workspace and singularities. The kinematic study reveals interesting features of this manipulator such as multiple working and assembly modes, small footprint and large workspace volume with high dexterity. Numerical examples of kinematic analysis are included. Practical application of the new manipulator is illustrated.

Digitalization of Musculoskeletal Risk Assessment in a Robotic-Assisted Assembly Workstation

The ergonomic assessment of adopted working postures is essential for avoiding musculoskeletal risk factors in manufacturing contexts. Several observational methods based on external analyst observations are available; however, they are relatively subjective and suffer low repeatability. Over the past decade, the digitalization of this assessment has received high research interest. Robotic applications have the potential to lighten workers’ workload and improve working conditions. Therefore, this work presents a musculoskeletal risk assessment before and after robotic implementation in an assembly workstation. We also emphasize the importance of using novel and non-intrusive technologies for musculoskeletal risk assessment. A kinematic study was conducted using inertial motion units (IMU) in a convenience sample of two workers during their normal performance of assembly work cycles. The musculoskeletal risk was estimated according to a semi-automated solution, called the Rapid Upper Limb Assessment (RULA) report. Based on previous musculoskeletal problems reported by the company, the assessment centered on the kinematic analysis of functional wrist movements (flexion/extension, ulnar/radial deviation, and pronation/supination). The results of the RULA report showed a reduction in musculoskeletal risk using robotic-assisted assembly. Regarding the kinematic analysis of the wrist during robotic-assisted tasks, a significant posture improvement of 20–45% was registered (considering the angular deviations relative to the neutral wrist position). The results obtained by direct measurements simultaneously reflect the workload and individual characteristics. The current study highlights the importance of an in-field instrumented assessment of musculoskeletal risk and the limitations of the system applied (e.g., unsuitable for tracking the motion of small joints, such as the fingers).

Kinematic study of a road power generator for the port transport network

Nowadays, energy-saving applications are based on alternative energy sources that enable autonomous powering of electrical consumers. Within the port transport network, 62% of freight transport is carried by road. One solution for the alternative generation of electrical energy for lighting and power supply of small power consumers is the use of road electromechanical systems such as artificial road bumps with an electromagnetic generator that converts the energy of vehicle movement into electrical energy. This article deals with a road power generator transducer with a slider-rocker kinematic pair for converting translational motion into rotational motion. The authors conducted a kinematic study of the actuating force transducer and analysed its performance at various connecting rod lengths with the required speed and dimensional criteria. They determined the effect of the connecting rod length on the trajectory and speed of the rocker arm. Analysis has shown that a connecting rod length of 100 and 150 mm, providing a working section with a uniform increase in speed of the rocker arm, satisfies the specified requirements. For further investigation of the electromechanical power system, the researchers adopted a 100 mm long connecting rod, as this allows the unit to be realised with reduced dimensions.

Direct kinematics of a manipulator with three mobilities

In the industrial halls it is often necessary to handle large objects, with a large and large table, which have to be transported not over long distances but moved from one place to another, raised, then lowered to various levels, left or right. Such repeated manipulations of heavy and dangerous objects can be done only with the help of a manipulator, which can be a crane, a specially designed trolley, a complicated robot or a simple manipulator as is the case for the one presented in the paper. The paper briefly presents the kinematic study of a manipulator with three mobilities, which can be used both in industrial halls and in garages, depending on its suitably chosen constructive size, which at smaller dimensions can be handled very easily. This manipulator can carry large loads, thus easing the work of the human being and preventing it from major dangers that can occur during the transport of large pieces and a large mass.

Six DOF Robotic Arm Prototype Modelling By Matlab

The study in this paper allows us to control the manipulator and achieve any desired position and orientation. The Forward Kinematics was done using Denavait Hartenberg (DH) parameters, also the forward kinematics equations and homogenous transformation matrix was validated using MATLAB Toolbox. The modeling was carried out using the Peter Corke robotics toolbox. Finally, the forward kinematic study and the robot arm’s movement equations were compared with practical measurements to make sure it fulfilled the desired purpose and that it could point to the desired coordinates with a precision of ±0.5 cm.

Effects of Femorotibial and Tibiotarsal Joint Ranges of Motion on the Gastrocnemius Muscle-Tendon Working Length in the Canine Cadaveric Limb

Objective This study aimed to describe changes in the length of the gastrocnemius muscle-tendon unit between the medial fabella and the calcaneus (MF-C) at different femorotibial joint (FTJ) and tibiotarsal joint (TTJ) angle combinations in the canine limb. Study Design This is an ex vivo kinematic study. Animals Canine cadaveric pelvic limbs (n = 11). Procedures One cadaveric pelvic limb was dissected to identify the anatomical origin and insertion of the gastrocnemius muscle-tendon unit for the radiographic landmark determination. The radiographic landmarks of the FTJ and TTJ were identified by lateral view radiographs. A series of lateral radiographs were evaluated to measure the linear MF-C at all combinations of the FTJ and TTJ angles. A mathematical model was defined for MF-C. Results The MF-C is associated with the FTJ and TTJ by a linear trigonometric relationship. Higher rate of increase in the MF-C was observed when the FTJ was > 135 degrees and the TTJ was < 125 degrees, compared with when the FTJ was <135 degrees and the TTJ was >125 degrees in all groups. Conclusions Thirty degrees of free range of motion of the TTJ between 140 and 170 degrees did not elongate MF-C in this cadaveric limb study. Clinical Relevance Some degrees of free range of motion may be possible in the TTJ during tendon healing based on our cadaveric study without causing excessive change in the MF-C, although this concept should not be applied until isometric contractions of muscles are clearly understood. The relationship between the MF-C and tension at tenorrhaphy should be evaluated.