Dynamic Modeling and Simulation of a Rotating Single Link Flexible Robotic Manipulator Subject to Quick Stops

Single link robotic manipulators are extensively used in industry and research operations. The main design requirement of such manipulators is to minimize link dynamic deflection and its active end vibrations, and obtain high position accuracy during its high speed motion. To achieve these requirements, accurate mathematical modeling and simulation of the initial design, to increase system stability and precision and to obtain very small amplitudes of vibration, should be considered. In this paper the modeling of such robotic arm with a rigid guide and a flexible extensible link subject to quick stops after each complete revolution is considered and its dynamical behavior analyzed. The extensible link which rotates with constant angular velocity has one end constrained to a predefined trajectory. The constrained trajectory allows trajectory control and obstacle avoidance for the active end of the robotic arm. The dynamic evolution of the system is investigated and the flexural response of the flexible link analyzed under the combined effect of clearance and flexibility.

Dynamical Analysis of a Constrained Flexible Extensible Link with Rigid Support and Clearance

Dynamic response of robotic systems is affected by deformation of their flexible components, velocity and mass of the systems, as well as by the presence of clearance or impact between the components. Since accurate simulations of such robotic systems are increasingly important, the modelling and dynamical behaviour of an extensible mechanism with a rigid crank and a flexible link is investigated in this paper. The equations of motion of the extensible flexible link, constrained to a circular, Cartesian, elliptical, Cassinian, Lame or pear-shaped quartic path, are presented. A dynamical analysis is carried out in order to compare the dynamical response of the flexible link vs. a rigid link under the combined effect of different parameters such as flexibility and clearance. The simulation result shows clear trajectories divergence due to the impact effect of the flexible link on the rigid crank

Students’ views and correlation regarding performance and attendance for a first year engineering cohort

This paper presents a case study to assess the students’ views and correlation between attendance to lectures, laboratories and seminars and their performance in terms of final results. The population is composed by a group of first year undergraduate students at the department of Design and Engineering, Bournemouth University, in an Engineering Design unit. Attendance was monitored for a number of 19 students over one academic year (2016-2017). Students’ views regarding the impact of some factors - such as clear expectations, content easy to understand, student collaboration and interaction, peer-pressure, and to be seen by the lecturer – on assessment performance have been surveyed. This data was obtained from a Likert-scale survey ran over a population of 10 students in the 2017-2018 academic year. The data that correlates final marks with attendance (laboratory, lectures and seminars) was analysed and indicates a strong least-squares fit correlation between attendance and final marks, with a coefficient of correlation R2=0.78 when plotting final marks vs overall attendance. Student view, which was also considered as an important aspect of this study, convey the benefits of attending the lectures and quantify some of the factors mentioned above including a minimum-maximum attendance rate for a good grade (first-class) or just a pass mark. Students perceive that the two main reasons for attending lectures are that, firstly, it makes it easier to understand the content and, secondly, they can get clear expectations on what they need to prepare and focus on

Kinematics and dynamics motion planning by polar piecewise interpolation and geometric considerations

The importance of numerical methods in science and engineering [Chapra, S.C., and R.P. Canale, “Numerical Methods for Engineers,” McGraw-Hill, 6th Ed., 2010] was long recognised and considered a fundamental factor in improving productivity and reducing production costs. The ability to model flexible systems and describe their trajectories [Gasparetto A., Boscariol P., Lanzutti A., Vidoni R., Trajectory planning in Robotics, Mathematics in Computer Science 6 (2012), pp. 269–279] involves usually the study of nonlinear coupled partial differential equations. Since their exact solutions are not normally feasible in practice, computational methods [V. Kumar, M. Zefran, J.P. Ostrowski, Motion Planning and Control of Robots, Handbook of Industrial Robotics, 2nd Edition, J. Wiley and Sons (2007), pp. 295–315] can be considered

Understanding the design variables that contribute to the response of a prosthetic foot: Part I –Rig Design

In this paper the design of a rig capable of replicating the dynamic response of an energy storing and returning composite prosthetic foot during amputee running is considered. It has been assumed that the amputee/prosthesis system can be modelled as a spring/mass system. Therefore the rig has been designed to allow the applied mass, input force frequency and foot contact point of various feet designs to be varied to test this assumption. The rig will allow the design variables that contribute to the response of a prosthetic foot during running to be understood and optimised to improve the foot’s performance

Understanding the design variables that contribute to the response of a prosthetic foot: Part II – Rig Validation

In this paper the validation of a rig capable of replicating the dynamic response of an energy storing and returning composite prosthetic foot during amputee running is considered. It is shown that the rig can effectively replicate the running action of an amputee runner and return the same ground contact time. It has also been shown that if a small input force is applied in a timed and sympathetic manner to the prosthetic spring-mass system the amplitude of oscillation increases which agrees with results of previous research. The rig will allow the design variables that contribute to the response of a prosthetic foot during running to be understood and optimised to improve the foot’s performance

Sensor-less control of a novel stepped hydraulic flow control valve

© 15th International Conference on Condition Monitoring and Machinery Failure Prevention Technologies, CM 2018/MFPT 2018. All rights reserved. This paper aims to create a sensor-less feedback position detection for a flow control orifice actuated by a stepper motor. Nowadays, many applications such as hydraulic and pneumatic systems use a stepper motor as an actuator, instead of traditional mechanical or solenoid. In nonlinear environment such as hydraulic systems, a stepper motor may suffer from step losing and leads to poor controllability of the system. Mechanical sensors are usually used as a feedback of the position and speed, but at the same time the harsh environment of hydraulic applications prevents implementing this kind of sensing. On the other hand, a sensor-less technique based on Kalman filter was used to control a stepper motor in different applications. This research represents a primarily investigation of the performance of Kalman filter in these for the valve based on modelling and simulation

Development of a wearable sensor system for dynamically mapping the behavior of an energy storing and returning prosthetic foot

It has been recognized that that the design and prescription of Energy Storing and Returning prosthetic running feet are not well understood and that further information on their performance would be beneficial to increase this understanding. Dynamic analysis of an amputee wearing a prosthetic foot is typically performed using reflective markers and motion-capture systems. High-speed cameras and force plates are used to collect data of a few strides. This requires specialized and expensive equipment in an unrepresentative environment within a large area. Inertial Measurement Units are also capable of being used as wearable sensors but suffer from drift issues. This paper presents the development of a wearable sensing system that records the action of an Energy Storing and Returning prosthetic running foot (sagittal plane displacement and ground contact position) which could have research and/or clinical applications. This is achieved using five standalone pieces of apparatus including foot-mounted pressure sensors and a rotary vario-resistive displacement transducer. It is demonstrated, through the collection of profiles for both foot deflection and ground contact point over the duration of a stride, that the system can be attached to an amputee’s prosthesis and used in a non-laboratory environment. It was found from the system that the prosthetic ground contact point, for the amputee tested, progresses along the effective metatarsal portion of the prosthetic foot towards the distal end of the prosthesis over the duration of the stride. Further investigation of the effective stiffness changes of the foot due to the progression of the contact point is warranted