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This paper demonstrates vibration reduction in a hollow rotating shaft by means of internal-stator active magnetic actuators, which are resiliently mounted. This problem requires further consideration over and above classic rotor/magnetic bearing systems on account of the flexible behavior of the magnetic actuator support structure. This paper presents an experimental facility conforming to the proposed topology, with a particular focus on the control problem such a system presents. The unique challenges are discussed, and a solution is presented in the form of H $_\infty$ -based control. Ultimately, experimental results demonstrate the system to be capable of substantial rotor vibration suppression, including while passing the rotor's first critical speed, which was not obtainable with simpler classical control techniques. This means the top achievable rotor speed was increased from approximately 3000 r/min without magnetic actuator vibration suppression to over 9000 r/min with vibration suppression active. At the rotor critical speed, the magnetic actuators affect a reduction in rotor vibration amplitude of over 70% compared to the rotor supported purely on mechanical bearings, while simultaneously avoiding excessive excitation of the flexible active magnetic actuator support structure.

Conventional multibody systems used in robotics and automated machinery contain bearing components that exhibit complex and uncertain tribological characteristics. These limit fundamentally the precision of the automated motion and also cause wear. Replacing traditional bearing joints with flexure couplings eliminates these tribological effects, together with wear, reducing necessary system maintenance and offering a potential for increased motion precision. A flexure-coupled multibody system is considered and a novel general solution technique is presented. Derivation of a large deflection flexure coupling model is provided and subsequently validated using an experimental facility. A focused study of a unique double-flexure-coupling rigid body system is given; the formulated nonlinear mathematical model can be used for feedforward control. Equivalent control is also applied to a corresponding system with traditional bearing joints. The feasibility of replacing bearing joints by flexure couplings is demonstrated in terms of accurate large displacement control and reduction of high-frequency disturbances.

A rotor spinning within an active magnetic bearing (AMB) system will normally be levitated and hence operate without rotor-stator contact. External disturbances and inherent unbalance may be compensated with appropriate control to keep rotor deviations within the clearance gap. However, AMBs have limited dynamic load capacity due to magnetic material field saturation. Hence overload conditions may result in rotor-stator contact. A touchdown bearing (TDB) and rotor landing sleeve are usually included to protect the expensive rotor, magnetic bearing and sensor components from damage. Once rotor-TDB contact has been made, rotor dynamic conditions may ensue resulting in persistent rotor bouncing or rubbing limit cycle responses. Prolonged exposure to these severe dynamics will cause TDB degradation and require regular replacement. If possible, a clear aim should be to restore contact-free levitation through available control capability in an efficient manner. This paper is used to guide the control options that are available to restore contact-free levitation. The use of AMB control is appropriate if the required control forces are within saturation limits. It is also possible to actuate TDBs and destabilize persistent rotor dynamic contact conditions. For example, piezo-based actuation offers larger control forces than those from magnetic bearing systems. Hybrid control action involving both types of actuation system has the greatest potential for completely robust restoration of contact-free levitation.

Typical rotor/active magnetic bearing (AMB) system layouts involving large, external stator AMBs may be difficult or inconvenient to apply to some rotor systems. Where space in the machine working envelope is at a premium, the space required by traditional AMBs may preclude them from inclusion in the design.

Hinged joints are ubiquitous in machine and mechanism design where components must rotate relative to one another. Their simplicity and reliability, coupled with limited alternatives, make them an obvious choice. However, the propensity of such joints to exhibit unpredictable discontinuities in their operation can limit the precision with which a mechanism incorporating such a joint can be controlled. In particular, almost all hinged joints experience some degree of both backlash and stiction. An alternative to hinged joints in many applications may be the use of large-displacement flexure-link joints. The use of flexure joints in micro-mechanisms is already an established practice, but their use in joints with large angular displacements (e.g. 30 degrees) is far less common. Such joints are inherently non-linear, and introduce more complex motion than simple hinges, but they offer the considerable advantage of highly predictable behaviour, without the exhibition of discontinuities. These characteristics open the way to increased mechanism precision and repeatability, and consequent new possibilities in machine design. This work makes a comparison of the precision which can be achieved when controlling similar mechanisms employing each of i) a realistic hinged joint, and ii) a large-displacement flexure-link joint. The modeling techniques used to represent each mechanism are discussed, and a series of results are presented illustrating the performance and prospects for precision motion of each system.

Conventional multi-body mechanisms used in robotics and automated machinery can have limited motion due to the bearing and transmission parts. Replacing a traditional bearing joint with a compact deformable structure (flexure coupling) can improve the performance envelope for a mechanism. A dynamic nonlinear mathematical model is derived for a mechanism comprising a flexure coupling, which can undergo large deformations, connected to a rigid link. Direct actuation of the mechanism is assumed in three directions and an open-loop control methodology is designed to regulate the actuation forces to achieve a prescribed path with precise and repeatable small scale motion. A mechanism containing a flexure coupling is examined and compared to that of an ideal hinge joint. The results show that a flexure coupling allows an increased range of motion for the mechanism compared to a hinge coupling and can have multiple paths in the x and y direction for a prescribed angle trajectory at the end of the mechanism.

Under normal operation a rotor spinning within an active magnetic bearing system will be levitated and hence rotor-stator contact conditions do not exist. In such a case, external disturbances and inherent unbalance will cause rotor responses that are maintained by the magnetic bearing control system to be within the clearance gap. However, magnetic bearings have limited dynamic load capacity due to magnetic material field saturation. Hence large external disturbances may be sufficient to cause the clearance gap to become closed and result in rotorstator contact. A touchdown bearing is usually incorporated as a sacrificial stator component to protect the expensive rotor, magnetic bearing and sensor components. Once contact has been made, rotor dynamic conditions may ensue resulting in persistent rotor bouncing or rubbing limit cycle responses. Prolonged exposure to these severe dynamics will cause touchdown bearing degradation and require regular replacement. A clear aim is therefore to restore contact-free levitation through available control capability in an efficient manner. This paper provides an analysis to gain an understanding of the uncontrolled rotor/touchdown contact dynamics. These will then be used to guide the control options that are available to restore contact-free levitation. The use of magnetic bearing control is appropriate if the required control forces are within saturation limits. It is also possible to actuate touchdown bearings and destabilize persistent rotor dynamic contact conditions. For example, piezo-based actuation offers larger control forces than those from magnetic bearing systems.

A novel rotor topology is proposed with the goal of reducing vibration in high speed rotor systems. Reduction in vibration at critical speeds is targeted. In essence, the novel topology consists of a hollow tube rotor coupled to a secondary non-rotating shaft located concentrically within the primary rotor. The two shafts are linked via a number of actively managed magnetic couplings. The topology is provided, along with an analysis comparing the out-of-balance vibration response of the proposed rotor to a comparable simple passive rotor. Designs for a test rig based on this topology are presented, together with an outline of anticipated testing and development of the idea. Special consideration is given to the design of the magnetic bearings, which form the system couplings. An internal-stator homopolar bearing design fabricated from soft magnetic composite is presented. The qualities of soft magnetic composite as a bearing core material are shown to be comparable with a standard laminated core with the added advantage of minimal eddy current losses within the primary rotor.

A topology composed of a hollow-shaft rotor on rolling element bearings coupled with internal-stator magnetic bearings mounted on independently supported flexible shafts is considered for the purposes of vibration reduction. Details of a bespoke test rig constructed to assess this topology are presented. The rig makes use of custom-designed internal-stator magnetic bearings fabricated from Soft Magnetic Composite material. Results from standard numerical analysis of the rig are given to demonstrate the expected behaviour of the system, with a particular focus on its potential to reduce synchronous vibration seen in the rotor while passing critical speeds. These behaviours are then confirmed via a series of experimental tests. These results show that the proposed topology can be used effectively to alter the system vibration behaviour.

A novel topology based on active magnetic bearing coupling for reducing synchronous vibration in rotors at critical speeds is outlined. The topology consists of a hollow rotor with a flexible concentric secondary shaft running along its length. Between the two shafts are one or more actively managed couplings. A design of a test rig to illustrate the effectiveness of the concept is presented, and results of finite element modelling on the rig are provided. It is shown that for the specific topology modelled, peak vibration amplitudes are around an order of magnitude lower than those of a decoupled rotor.

Purpose: To determine the perceptions of educators and students in Canadian entry-level professional physiotherapy programmes with respect to the current draping curriculum and the methods of delivery of that content and to determine if there is a need for additional draping education time and resources in these programmes. Methods: Canadian university physiotherapy students (n=127) and educators (n=183) completed questionnaires designed by the authors. Data were collected via Survey Monkey, exported as Excel files, and analyzed using descriptive statistics and Pearson chi-square analysis. Results: Students and educators agreed that dignity as a concept and draping as a skill to protect patient dignity are both important and should be included in Canadian physiotherapy curricula. Respondents also agreed that students often have difficulty with draping. Educators identified barriers to teaching draping while students identified components of an effective educational resource on draping. Conclusions: To enhance the development of effective draping skills among entry-level physiotherapists, draping education should be included in Canadian physiotherapy curricula. An effective draping educational resource should be developed for educators and students.

Specific-pathogen free chickens were infected with the RB1B strain of Marek's disease virus (MDV) and T cells from the spleens of infected as well as age-matched controls were fractionated by flow cytometry at 4, 10, and 21 days post-infection (d.p.i.). Real-time quantitative reverse transcription PCR was used to assess the amount of cytokine transcripts as well as viral genes meq and glycoprotein B (gB). There was an increase in the number of CD4(+) T cells, as well as a significant increase in the expression of the viral meq gene in CD4(+) T cells, which coincided with the presence of tumors in various organs of infected birds. It was also observed that there was a significant upregulation in the amount of the gene expression of interferon (IFN)-gamma, interleukin (IL)-18, and IL-6 at 4 and 21 d.p.i. in CD4(+) and CD8(+) T-cell subsets. The expression of IL-10 was upregulated as well. The outcome of the cytokine milieu inclined towards the induction of a type I immune response at 4 and 21 d.p.i. Our study indicates that MDV-associated cytokine profiles vary in CD4(+) and CD8(+) T-cell subsets, and that cytokines including IFN-gamma, IL-18, IL-6, and IL-10 may play a role in the elicitation of an immune response to MDV.