Transactions of the Canadian Society for Mechanical Engineering
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Volume 40 (2016), Issue 2
Guest Editorial: Special Issue on Mechanisms, Machines and Mechatronics
M. John D. Hayes, Eric Lanteigne
A pitch-roll joystick based on a spherical cam mechanism is proposed that can be implemented as a haptics device. Spherical cams can replace the bevel gears that are conventionally used in transmission mechanisms involving shafts with intersecting axes to achieve lower backlash, lower frictional losses and higher stiffness. Such a spherical cam mechanism is essentially composed of multi-lobe-cams and conical rollers. Undercutting is a deterrent to the generation of smooth cam surfaces, which calls for the synthesis of a singularity-free spherical cam profile. The issues of high pressure angle and high contact ratio are addressed by means of a multilobe cam. The design of the cam profile and the assembly of the joystick are described. The criteria for the selection of the numbers of lobes and rollers are also explained.
Parametric trajectory optimisation for increased payload
André Gallant, Clément Gosselin
The load-carrying capacity of manipulators is often considered to be the same throughout their workspace. However, the actual capacity of manipulators largely depends on their posture, their velocity, their acceleration and the limits of their actuators. In this paper, a method is proposed to increase the payload capacity of manipulators through trajectory optimisation. This optimisation is performed on a task basis and therefore, the load-carrying capacity varies from task to task. An extensive analysis of the method is conducted based on its application on a planar RR serial two degree-of-freedom manipulator. This analysis evaluates the ability of the method to find feasible trajectories and compares the results with those obtained using Bang-bang type methods. It is shown that, although the trajectories produced by the proposed method are not time optimal, the method is much more versatile and much simpler to implement than its Bang-bang counterparts.
An interval analysis method for wrench workspace determination of parallel manipulator architectures
Joshua K. Pickard, Juan A. Carretero
This paper deals with the wrench workspace (WW) determination of parallel manipulators. The WW is the set of end-effector poses (positions and orientations) for which the active joints are able to balance a set of external wrenches acting at the end-effector. The determination of the WW is important when selecting an appropriate manipulator design since the size and shape of the WW are dependent on the manipulator's geometry (design) and selected actuators. Algorithms for the determination of the reachable workspace and the WW are presented. The algorithms are applicable to manipulator architectures utilizing actuators with positive and negative limits on the force/torque they can generate, as well as cable-driven parallel manipulator architectures which require nonnegative actuator limits to maintain positive cable tensions. The developed algorithms are demonstrated in case studies applied to a cable-driven parallel manipulator with 2-degrees-of-freedom and three cables and to a 3-RRR parallel manipulator. The approaches used in this paper provide guaranteed results and are based on methods utilizing interval analysis techniques for the representation of end-effector poses and design parameters.
Derivation and validation of a spatial multi-link human postural stability model
Nicholas R. Bourgeois, Robert G. Langlois
In naval engineering and related disciplines, it is common for dynamic models of the human body to be used in conjunction with quantitative records of body and ship motions, in order to study human balance behaviour while performing various shipboard activities. Research in this area can lead to improvements in ship operations and designs that improve crew safety and efficiency. This paper presents the development of a new spatial 18 degree-of-freedom (DOF) ship-inverted pendulum model that incorporates 6 DOF ship motion and 3 DOF joints representing ankle, knee, hip, and neck motions. The derived model is then validated by comparing it to similar models derived using alternative methods but simulated under equivalent input conditions.
Design and development of an autonomous omnidirectional hazardous materials handling robot
Nicholas Charabaruk, Scott Nokleby
This paper describes the design and testing of an autonomous omnidirectional robot to be used for moving radioactive materials while minimizing human exposure. The robot, called the OmniMaxbot, uses the Robot Operating System (ROS) to allow the individual components to communicate as well as to control the movement. Details about the hardware and software used in the OmniMaxbot are explained. Test results are presented for the navigation system based on the ROS packages: Global Planner, Base Local Planner, and Adaptive Monte Carlo Localization (AMCL). The test results confirm that the OmniMaxbot is capable of autonomously navigating to a mock ash can, lifting it, navigating to a drop-off location, putting the mock ash can down, backing away until the forks are clear of the mock ash can, and navigating to a standby location. These actions can be performed in areas with both static and dynamic obstacles.
Trajectory optimization of a small airship in a moving fluid
Charles Blouin, Eric Lanteigne, Wail Gueaieb
Airships offer a low-cost alternative to heavier-than-air vehicles for long endurance applications in surveillance and transport. Although manoeuvring an under-actuated vehicle in a real environment while taking into account the obstacles, the dynamical model, the wind, and the energy consumption has been studied extensively, planning complex manoeuvres in constrained environments remains an active research area. This paper examines the use of optimal control for the trajectory planning of a small airship. The dynamic model of the vehicle and the experimental characterization of the drag coefficient are presented first, followed by the description of the trajectory planning problem formulated as an optimal control problem. Two trajectories are then solved using a pseudo-spectral solver to demonstrate that an optimal control approach can be used to generate complex and realistic manoeuvres.
Design of a vision guided mechatronic quadrator system using design for control methodology
Abolfazl Mohebbi, Sofiane Achiche, Luc Baron
Designing mechatronic systems is known to be both a very complex and tedious process. This complexity is due to the high number of system components, their multi-physical aspects, the couplings between different engineering domains and the interacting and/or conflicting design objectives. Due to this inherent complexity and the dynamic coupling between subsystems of mechatronic systems, a systematic and multi-objective design approach is needed to replace the traditionally used sequential design methods. The traditional approaches usually lead to functional but non optimal designs solutions. In this paper, and based on an integrated and concurrent design approach called "Design-for-Control" (DFC), a quadrotor UAV equipped with a stereo visual servoing system is used as a case study. After presenting the dynamics and the control model of the Quadrotor UAV and its visual servoing system, the design process has been performed in four iterations and as expected, the control performance of the system has been significantly improved after finishing the final design iteration.
Energy harvesting using a nonlinear vibration absorber
Yu Zhang, Riccardo De Rosa, Jingyi Zhang, Mariam Alameri, Kefu Liu
In this study, an energy harvesting device based on a nonlinear vibration absorber is developed to achieve two objectives: vibration suppression and energy harvesting in a wideband manner. First, the proposed design is described. Next, the system modeling is addressed. The parameter characterization is presented. Then, the performance of the nonlinear vibration absorber is tested by sweeping harmonic excitation. The testing results have shown that the device can suppress vibration and convert vibration energy into electric energy in a broadband manner.
Mechatronics design of an X-by-Wire prototype of an electric vehicle
Mir Saman Rahimi Mousavi, Guillaume Sauze, Alexei Morozov, Jorge Angeles, Benoit Boulet
The concept of electric vehicle as a fully automated mobile robot – a.k.a. X-by-Wire, or Drive-by-Wire (DbW) concepts – is becoming more and more attractive in the modern automotive industry. This idea is based on replacing a mechanical subsystem by its electronic equivalent, which includes sensors and actuators, with a computer in-between. Three of the components, namely Throttle-by-Wire, Brake-by-Wire, and Steer-by-Wire, are the most complex and risky elements of the X-by-Wire technology. Moreover, these elements constitute the inherent part of the general DbW paradigm. This paper reports work-in-progress on the design and prototyping of a scaled-down 1 : 6 proof-of-concept model of a commercial vehicle with an integrated X-by-Wire system. The control for its components is discussed, while emphasizing the Steerby- Wire actuator based on the Ackermann condition. The influence of heading velocity and turning angle on the slipping angle and path error of the model is discussed. The performance of the dynamics of the prototype is assessed over prescribed paths; deviations from the no-slip condition are evaluated.
Design of a spherical cam-roller mechanism for an automotive differential
Mayank Chaudhary, Jorge Angeles, Alexei Morozov
Spherical cam-follower mechanisms are attractive alternatives to bevel gears, as they provide low backlash and low friction losses. The design of such a mechanism is reported here, to be incorporated in an automotive differential, whose bevel pinions and side gears are substituted by spherical cams and rollercarriers, respectively. Critical to the design of cam mechanisms is the generation of the cam-profile, free of undercutting. The profile, generated using computer algebra, is analyzed for singularities, including cusps and double points. The pressure angle, an important factor that governs the effective force transmission of cam mechanisms, is duly kept within acceptable limits. Conclusions are drawn on the suitability of cam mechanism developed for automotive applications.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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