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Reconfigurable composite joints (RCJs) are essential elements in the design of reconfigurable mechanisms. One significant trend is to synthesize RCJs with pre-specified motion properties. This paper focuses on the general synthesis method for the design of RCJs based on motion decomposition and reconstruction (MDR). The overall concept of MDR targeting the design of RCJs is first introduced. Then, the concept and its application are described, including six steps: (i) determination of the main chain (MC); (ii) motion modeling of the MC; (iii) analysis and decomposition of the total motion of the MC; (iv) reconstruction of the chains with different submotions by means of auxiliary chains (ACs); (v) determination of the pertinent adjustable chain, and assembly of the MC, ACs, and the adjustable chain; and (vi) layout of the actuation scheme. Subsequently, three kinds of RCJs with different main chains are generated systematically by means of the concepts proposed herein. Finally, one reconfigurable parallel-kinematics machine (PKM) with one proposed RCJ in a limb is used as an example, which offers applications in the design of reconfigurable mechanisms. The proposed concept, MDR, is not only suitable for type synthesis of simple kinematic chains, but also potentially applicable to reconfigurable kinematic chains.

A symmetric, double-tripod multi-loop mechanism (DTMLM), for aerospace applications, is the subject of this paper. Its mobility and singularity are analyzed, while introducing a novel tool, the cell-division method for singularity analysis, applicable to multi-loop mechanisms. The key principle of this method lies in replacing the singularity analysis of the original multi-loop mechanism with: (1) that of an equivalent simpler parallel mechanism; (2) the constraint analysis between loops; and (3) the singularity analysis of simpler kinematic subchains. Then, the mechanism is transformed into a simpler, equivalent parallel mechanism with three identical kinematic subchains. Its mobility and singularity are analyzed based on screw algebra, which leads to a key conclusion about the geometric properties of this mechanism. Results show that: (a) the DTMLM has three degrees of freedom (dof), i.e., two rotational dof around two intersecting axes lying in the middle plane of the mechanism, and one translational dof along the normal to the said plane (2R1T); and (b) the singularities of the 3-RSR parallel mechanism are avoided in the DTMLM by means of prismatic joints, singularities in the DTMLM occurring on the boundary of its workspace. Thus, the DTMLM has a 2R1T mobility everywhere within its workspace. When a set of multi-loop mechanisms of this kind are stacked as modules to assemble a multi-stage manipulator for space applications, the modules can be designed so that, under paradigm operations, all individual loops operate within their workspace, safe from singularities.

The authors propose a model of the elastodynamics of the Peppermill Carrier, a parallel isostatic Schönflies-motion generator designed for pick-and-place operations. The Cartesian spring and the finite element method are used to build the elastodynamics model of the robot. The stiffness and mass matrices are introduced to obtain the natural frequencies of the robot along a test trajectory — the Adept test cycle — that serves to evaluate the performance of the robot with respect to the operation speed.

A micro/meso-scale monolithic architecture was designed, fabricated and tested for in-plane inertial sensing and actuation with isotropic stiffness in the sensitive plane and high frequency-ratios between the insensitive and sensitive directions. The architecture was designed to accommodate any regular polygonal shape with a proof-mass suspension made of a serial array of compliant parallelogram linkages. Structural optimization and finite element analysis were conducted to achieve high frequency ratios and a high degree of compliance in the sensitive directions, for low-g applications and in-plane sensing. Then, the elastically isotropic structure for any regular polygonal shape was modeled in the sensitive plane and validated numerically. Lame curves were introduced in the fillets to relax the stress concentration, while air-damping analysis was introduced to provide prediction of the high resistance in the insensitive out-of-plane motion. Next, the microfabrication process was devised and conducted for triangular and square structures based on the biaxial architecture. Special techniques were studied on the wafer bonding with large cavities and the adhesive influence during deep reactive-ion etching (DRIE). Finally, techniques were studied on the reflectivity adjustment of the sample surface and the in-plane biaxial motion detection of the fundamental frequencies using a uniaxial laser-sensing system. Vibration tests conducted in the micro/meso prototypes validated the isotropic biaxial sensitivity and the size effect of the high squeezed-film air damping in the insensitive direction.

In order to avoid motor saturation in turning maneuvers, an iterative Lame-trajectory planning scheme is proposed to generate a smooth curvature-bounded transition trajectory for a differential-driving wheeled mobile robot (DWMR) switching from one straight path to another. The scheme consists of Lamecurve blending, inverse-kinematics computation, peak-torque positioning and torque-saturation avoidance. Firstly, a Lame-curve blending procedure based on affine transformations, is formulated to generate a smooth G2-continuous transition trajectory for connecting two straight paths. Secondly, the platform twist is calculated according to the curvature of the Lame-curve trajectory, then transformed into the actuated-joint rates by means of the inverse-kinematics model. Thirdly, a peak-torque positioning technique is developed to estimate the peak torques of the driving wheels when the DWMR tracks the trajectory, by combining the computed-torque method and the inverse-dynamics model. Finally, an iterative r-step saturation-avoidance prediction planning strategy is devised to suppress the peak motor torques, by means of two torque limitation schemes via adjusting trajectory curvature and robot speed. The simulation results show that, compared with the conventional planning techniques for circular arcs, our trajectory planning scheme can generate a smooth saturation-free transition trajectory with feasible curvature and traveling speed. The scheme is significantly beneficial for trajectory tracking under finite actuation torque in turning maneuvers, thereby preventing any possible path deviation caused by insufficient torque.

This article addresses the path synthesis of RCCC (revolute-cylindrical-cylindrical-cylindrical) linkages, a problem that has not received due attention in the literature. Compared with planar and spherical four-bar linkages, a RCCC linkage has many more design parameters, which lead to a complex formulation of the path synthesis problem and, consequently, to a quite challenging system of algebraic equations. In this article, the problem is solved with a novel formulation of path synthesis for visiting a number of prescribed positions. This is achieved by means of an alternative coordinate system, which allows point coordinates to be expressed with the aid of two vectors fixed to the same body. By this means, the rotation matrix used to represent the coupler link attitude is obviated. The synthesis equations are then formulated in a simple form. Our formulation confirms that path synthesis admits exact solutions for up to nine prescribed positions, which proves a landmark claim submitted by Burmester. Examples are included to demonstrate the path synthesis procedure with the method thus developed.

A three-dof 2 P UR-2R P U redundantly-actuated parallel-kinematics machine, designed for the machining of complex curved surfaces that require high-speed and high-precision, is the object of study in this paper. The lower-mobility PKM, consisting of two pairs of symmetric, limited-dof limbs, has the advantages of high stiffness, simple kinematic chain, and reduced singularities. The mobility of the robot is investigated via Lie-groups, instead of the well-known Chebyshev–Grubler–Kutzbach formulas, which are not applicable to our case. Then, the inverse-displacement, direct-displacement and corresponding velocity relations are analyzed in detail. Next, by investigating the rank-deficiency of the corresponding Jacobian, three types of singularities, those associated with direct-kinematics, inverse-kinematics and combinations thereof, are analyzed in depth, while constraint singularities are investigated by resorting to constraint wrenches. Moreover, the workspace of both the reference point P and the tool head, when a tool is added to the moving platform, are derived. It is noteworthy that the local and global dexterity indices are evaluated by resorting to the characteristic length to homogenize the dimensionally inhomogeneous Jacobian matrix at hand, then the condition number is minimized over the independent posture parameters and the characteristic length via the first-order normality conditions.

The design of the contact profiles of spur gears with involute teeth is well developed, with industry standards that set values for pressure angle and ratios for virtually all dimensions. This is not the case for bevel gears, where involute teeth, although known for several years, haven’t been adopted by industry. As a result, no standards for involute bevel gears are available. In the case of hypoid gears, owing their name to the pitch surfaces, the definition of involute surfaces is still to be seen. This state of affairs motivated the authors to look for alternative means of synthesizing the contact profiles of interest. Reported in this paper is the application of the Camus Theorem to the synthesis of the contact profiles of spur (planar)- and bevel (spherical)-gear teeth. It is shown that, upon using the planar or, correspondingly, the spherical logarithmic spiral as auxiliary centrode, the contact profiles of spur and bevel gears with involute teeth can be obtained within a unified framework.

The authors report a novel MEMS capacitive sensing structure that utilizes a single-layer electroplated gold to achieve simultaneous sensing of biaxial acceleration with low cross-axis sensitivity. The capacitive sensing structure is designed for the in-plane biaxial accelerometer with high frequency ratio and low-g acceleration range. The etching precision of the large proof-mass suspension is guaranteed by the design of detachable supporting islands. Then, different locations are explored in arranging the capacitors, for which the corresponding estimation algorithms are derived. Finally, the proposed structure was fabricated under the commercial MicraGEM-Si platform based on silicon-on-insulator (SOI) technologies. In summary, the structural and fabrication designs of the MEMS capacitive sensing structure solve the problems in biaxial independent sensing, while offering: 3D connectivity of electrodes using planar fabrication technologies; large proof-mass fabrication precision; identical mobility range in all in-plane directions; and sensing algorithms for any regular polygonal shape.

Tracked vehicles have inherent advantages over wheeled vehicles, as the former provide stable locomotion on loose and uneven terrain. However, compared with the latter, the slippage generated due to the complex, nonlinear track-terrain interactions during skid-steering to follow a curve, brings about difficulties preventing the accurate prediction of their motions. The key to improving the accuracy of trajectory-following is the “proper” motion control methodology that can accurately factor-in the slippage behavior. In this paper, the authors propose a novel approach to the dynamic modeling and motion control of tracked vehicles undergoing skid-steering on horizontal, hard terrain, under nonholonomic constraints. Due to the skew-symmetry property of nonholonomic mechanical systems, the control methodology is established using the backstepping method based on a modified Proportional–Integral–Derivative (PID) computed-torque control. A key element in the control strategy proposed here is the reliable estimation of the pose – position and orientation – of the vehicle platform and its twist—point velocity and angular velocity. It is assumed that the vehicle is suitably instrumented to allow for accurate-enough pose and twist estimates. Validated via a numerical example, the proposed controller is proven to be effective in controlling an unmanned tracked vehicle.

Least-square problems arise in cases involving arrays with entries bearing different units, rather common in the analysis and synthesis of mechanical systems. Indeed, this is the case with rigid bodies whereby both rotation and translation occur. Dual numbers have been extensively used to take into account this feature. However, the primal part of the system of equations is still usually solved first, followed by the dual part. In this paper, we propose the use of the concept of characteristic length to be able to obtain one single dimensionless system of equations in problems of kinematic synthesis where the least-square solution to a system with both rotation and translation is to be found.

Pick-and-place robots are used to complete many tasks in industry, from packaging operations to manufacturing. Schonflies-motion generators (SMG), capable of three translations and one rotation about an axis of fixed direction, are commonly used for this purpose. Many researchers have focused in recent years on finding new mechanisms to reduce the time necessary to complete a pick-and-place operation, as well as providing a higher rotability of the mobile platform, an issue that handicaps several SMGs. In this paper, the workspace of a parallel isostatic SMG, with virtually unlimited rotability, is analyzed in order to optimize a paradigm trajectory with the objective of reducing the torque needed from the motors, thus allowing for higher operation frequencies. The paradigm path is kept unchanged, but the starting-point location is optimized. It is shown this location significantly affects the maximum absolute torque required to cross the same distance with the same cycle time.

The authors report on the design, configure, and test of isotropic accelerometer strapdowns for high-precision inertial measurement unit (IMU) and folded MEMS configuration. The biaxial low-g MEMS accelerometers are based on the Platonic solids. A Platonic strapdown is integrated into an embedded system for acceleration-array signal acquisition targeting rigid-body pose-and-twist estimation. The electromechanical properties for dynamic sensitivity are tested on a haptic manipulator, which shows that the position estimation matches reasonably well the encoder readouts. The Platonic strapdown is promising in folded MEMS IMU with chip-level miniaturization and high estimation precision.

Novel catheter-based medical procedures targeting heart valve structures are currently under development. These techniques entail installing a prosthetic implant on valves inside a beating heart. The development of these approaches requires a simple and effective validation test bed. Current early process testing methods rely on both static and dynamically pressurized excised porcine hearts. The variability between excised-tissue mechanical properties poses problems of reproducibility. In addition, these test beds do not emulate annulus motion, which affects the implant installation. A reproducible phantom of the left atrioventricular chambers was developed. The system consists of a hydraulic constant flow arrangement and a polyvinyl alcohol phantom heart with material properties that mimic passive myocardium mechanical properties and annulus motion. The system was then used to emulate blood flow through an actual heart. The building process starts by obtaining an accurate computer-aided design (CAD) model of a human heart, from which, a mold is produced using a novel rapid-freezing prototyping method and computer numerical control machining. The phantom is then cast-out of polyvinyl alcohol (PVA), a hydrogel, whose mechanical properties are set by subjecting the phantom to freeze and thaw cycles. Subsequently, blood flow is emulated at a constant volumetric rate at the atrial pressure observed in a healthy adult human heart at rest. The annulus motion is implemented by suturing the outside of the phantom to a one-degree-of-freedom cam-follower mechanism reproducing valve motion. Such test beds could play a significant role in future development of medical devices.

The kinematic analysis of the planar motion of vehicles, such as common cars, buses, and trucks, when traveling along linear and circular tractrices at low speeds, is proposed here based on the fundamentals of the kinematics of planar mechanisms. In particular, the analysis of the vehicle chassis motion, with chassis represented as a drawbar connecting the back and front-wheel centers, is developed and formulated by determining the moving and the fixed centrodes. The proposed formulation was implemented in matlab to simulate and analyze the vehicle motion at low speeds, as the front-wheel center follows a straight line or a circle and, correspondingly, the back-wheel center traces a linear tractrix or one of the inner and outer circular tractrices, according to the exit from or entrance of the vehicle into a roundabout. Significant numerical and graphical results allow the validation of the proposed formulation, which represents useful tool to predict the vehicle behavior at low speeds during parking, changing of lanes, and entering and leaving roundabouts, thereby increasing the safety for bicycles, motorcycles, and pedestrians, along with the design of safe roads and highways.

The design process starts with a need, as spelled out by the client. In engineering design, as well as in other design areas, the need is described by the client in rather ambiguous, fuzzy, sometimes contradictory terms. After a series of exchanges between client and designer, be this an engineer, an industrial designer, or an architect, the need is formulated in terms of a list of functional requirements, with some specific features that are spelled out as design specifications, or specs for brevity.

The subject of this paper is the elastodynamics of a novel three-limb, full-mobility parallel-kinematics machine (PKM) with flexible links, intended for high-frequency, small-amplitude operations. By modeling the light-weight limb-rods as identical linearly elastic beams, the flexibility of the in-house developed SDelta robot is taken into account. The PKM is modeled as a six-dof Cartesian mass-spring undamped system. The Cartesian stiffness and mass matrices are derived based on the virtual-joint model. The elastodynamics performance of the SDelta prototype at the desktop scale is numerically evaluated. The calculation results shows that the prototype has the ability to operate at a frequency below 30 Hz with a 5-kg payload.

The linearized Cartesian elastodynamics model of mechanical systems with flexible links is introduced in this paper to simplify its counterpart n -dof generalized model. The stiffness is represented by means of Loncaric’s 6 × 6 Cartesian stiffness matrix (CSM), the inertia by what von Mises termed the inertia dyad, i.e., the 6 × 6 Cartesian mass matrix (CMM). This model applies to a mechanical system with compliant components. Furthermore, the Cartesian frequency matrix (CFM) is defined as a congruent transformation of its stiffness counterpart, the transformation matrix being the inverse of the square root of the positive-definite CMM. The CFM thus defined is dimensionally-homogeneous, symmetric and at least positive-semidefinite. Upon the eigenvalue decomposition of the same matrix, the natural frequencies and the corresponding natural modes, i.e., the eigenscrews of the system, are obtained. The physical meaning of the CFM, together with that of its eigenvalues and eigenscrews, are given due interpretation in the paper, within the context of screw theory. This matrix is intended to serve as a useful tool for the elastodynamics analysis and design of a large class of multibody systems with flexible components, especially at the early design stages.

Recent developments in electric vehicles incorporate multi-speed transmissions to improve the electric vehicle range and performance. Similar to transmissions for fossil-fuel vehicles, those for their electric counterparts undergo topology changes during gear-shifting. However, this important phenomenon has been overlooked in the development of transmission mathematical models, which results in unrealistic prediction of the transmission dynamic response. In this study, a topology-change model based on the impulse-momentum relation is developed to address the topology change of multi-speed transmissions in electric vehicles during gear-shifting. An orthogonal complement is introduced to eliminate the non-working constraint forces. The velocity jump brought about by topology changes is given due attention. A case study is included, whereby the model is applied to a novel modular multi-speed transmission for electric vehicles. First, tests are conducted on the transmission experimental testbed; then, the test results are reproduced in simulation using the model developed herein. Moreover, the velocity jump of the gear-shifting is computed by means of the model. Subsequently, simulation of the transmission gear-shifting incorporating the velocity jump is conducted. By means of the model developed in this paper, a more realistic prediction of the transmission dynamic response can be achieved. Moreover, this model can be applied to any vehicle transmissions with gear-shifting, such as dual-clutch transmissions (DCTs).

The subject of the paper is the optimization of the pose of redundant spherical parallel manipulators (SPMs) performing pointing tasks, i.e., orienting a line in space; a few hints for the synthesis of dextrous machines are also provided. The strengths of parallel mechanisms are often limited by their singular configurations; to overcome this problem, a class of SPMs with 3-RFR topology (Revolute-Planar-Revolute pairs for each of the three limbs) is investigated, with a comprehensive analysis to identify their singular configurations. The geometric parameters of the architectures are chosen in such a way that all kinds of singularity surfaces come to coincide and a single 3 × 3 Jacobian matrix is able to describe all the singular configurations of the machines. Then, singularities are avoided by exploiting the functional redundancy of the manipulator with respect to the task: an optimization algorithm allows the user to find, for each pointing direction, the robot posture that yields the highest dexterity. Finally, an optimal path is traced on the surface of the sphere of motion by finding the Bezier curve that minimizes a task performance index. The kinematic analysis and optimization are worked out by using a robust formulation based on rotation invariants that allows for a straightforward generalization of the results obtained.

The research work reported here was motivated by a class of two-limb parallel Schonflies-motion 1 generators, which offer simplicity, isostaticity, and symmetry. The crucial components required to construct a parallel two-limb robot of this class are a cylindrical drive, namely, a cylindrical motion generator, and a load-carrying link playing the role of the moving platform in parallel robots, with four degrees-of-freedom, i.e. 3D translation and rotation about a vertical axis, which operates based on the same cylindrical motion generator. However, the design requirements of such components call upon screw joints with an unusually large pitch, which are not available off-the-shelf; the authors thus propose a cable-driven virtual screw with an arbitrarily large pitch. This concept is elaborated on with regard to its various alternatives, each suitable for different circumstances and applications. Furthermore, the concept of variable-pitch virtual screw is introduced, which enables the designer to adapt the specification of the robot to any given task. In addition, the novel application of the virtual screw in the context of the architecture of Schonflies-motion generators is studied. Finally, the authors report the design and fabrication of two prototypes to conduct a comparison between the screw joint and the virtual screw.

The efficiency of electric vehicles (EVs) can be improved by applying multi-speed transmissions (MSTs), while ensuring that gear-shifting is swift and smooth. This paper establishes a gear-shifting control algorithm for a novel MST, with the advantages of simplicity and modularity, designed for EVs. Firstly, the mathematical model of the proposed MST is derived. Next, the control algorithm developed for gear-shifting is clarified, which guarantees seamlessness and swiftness. The system under study is over-actuated, with end constraints on some control inputs. Therefore, for acceleration and jerk continuity, while satisfying the input terminal constraints, one input is suggested to be changed independently, based on a 2-3 blending polynomial. Then, the new fully-actuated system is controlled using a linear quadratic integral (LQI) controller, which is an extension of the linear quadratic regulator (LQR) for tracking problems. Simulation results indicate the effectiveness of the proposed control algorithm in the presence of unknown external disturbances.

Sudden failure and rupture of the tissue is a rare but serious short-term complication after the mitral valve surgical repair. Excessive cyclic loading on the suture line of the repair can progressively damage the surrounding tissue and finally cause tissue rupture. Moreover, mechanical over-tension, which occurs in a diseased mitral valve, gradually leads to tissue floppiness, mitral annular dilation, and leaflet rupture. In this work, the rupture mechanics of mitral valve is studied by characterizing the fracture toughness exhaustion of healthy tissue. Results of this study show that fracture toughness of the posterior mitral valve is lower than its anterior counterpart, indicating that posterior tissue is more prone to failure. Moreover, the decrease in fracture toughness by increasing the number of fatigue cycles shows that excessive mechanical loading leads to progressive failure and rupture of mitral valve tissue within a damage accumulative process.

The 3- C CC class of parallel-kinematics machines (PKMs) bears many interesting features, as found in a previous paper on its optimum design. In this paper, its forward-kinematics (FK), singularity, workspace and dexterity analyses are studied. FK reveals that the rotation and translation of the moving platform (MP) are decoupled at the displacement level; moreover, a simple formulation is derived for the orientation subproblem that admits up to eight solutions, which is minimal; a quartic resolvent polynomial for the FK is then derived. All solutions thus can be found simultaneously in closed-form, while the computational cost is reduced; this brings robustness, especially when the robot operates near a singular configuration. Next, the translation problem is solved from a linear-equation system. These features, rare in six-dof PKMs, greatly simplify its simulation and control. Next, the singularity in question is shown to be determined solely by the orientation of the MP, thereby simplifying dramatically its evaluation and representation. Furthermore, the robot is shown to bear position and orientation workspaces of reasonable size, together with high dexterity. These features make the proposed PKM class quite promising in a variety of applications.

The design for isotropy of a large class of six-dof parallel-kinematics machines (PKMs) whose six actuated wrenches intersect pairwise, is the subject of this paper. A PKM is called isotropic when it can achieve one or more postures under which the condition number of its Jacobian matrices becomes unity, thereby offering a high positioning accuracy. Based on a symbolic expression of the inverse of the forward Jacobian matrix, we analyze the isotropy condition for this class of PKMs. It is shown that isotropy can be achieved only when the moving platform (MP) bears an equilateral-triangular shape; however, the operation point need not be the centroid of this triangle. Moreover, for a MP with an acute-triangular shape, there exist postures that we call quasi-isotropic, under which the condition number is close to unity, while the six rows of the Jacobian matrix are mutually orthogonal. This greatly enriches the list of candidates for the MP shape and the location of the operation point, required, e.g., when a gripper or another tool is attached to the MP triangle.

The Euler–Rodrigues parameters (ERP) are revisited in this paper, the motivation being the need for a systematic methodology to formulate the inverse-displacement problem associated with a six-revolute (6R) serial robot. Although significant progress was made in the solution of the problem in the eighties and nineties, there is not one algorithm adopted by the research and applications communities, but rather various algorithms that lead to the resolvent polynomial of 16th degree or lower. In this paper the problem is formulated using the dual ERP. Motivated by the lack of a methodology that would allow R&D professionals to readily implement a generic solution algorithm in industrial environments requiring real-time inverse-displacement problem (IDP) solutions. An inverse-displacement numerical solution of 6R robots of arbitrary architecture is proposed. This is the main thrust of the paper. The contribution of the paper is a systematic procedure to formulate the problem and implement its solution by numerical means. The procedure is illustrated with the example of an industrial robot whose architecture does not allow for a closed-form solution.

In light of the current low energy-storage capacity of electric batteries, multi-speed transmissions (MSTs) are being considered for applications in electric vehicles (EVs), since MSTs decrease the energy consumption of the EV via gear-shifting. Nonetheless, swiftness and seamlessness are the major concerns in gear-shifting. This study focuses on developing a gear-shifting control scheme for a novel MST designed for EVs. The main advantages of the proposed MST are simplicity and modularity. Firstly, the dynamics model of the transmission is formulated. Then, a two-phase algorithm is proposed for shifting between each two gear ratios, which guarantees a smooth and swift shift. In other words, a separate control set is applied for shifting between each gear pair, which includes two independent PID controllers, tuned using trial-and-error and a genetic algorithm (GA), for the two steps of the algorithm and a switch. A supervisory controller is also employed to choose the proper PID gains, called PID gain-scheduling. Simulation results for various controllers and conditions are reported and compared, indicating that the proposed scheme is highly promising for a desired gear-shifting even in the presence of an unknown external disturbance.

The optimum design of a biaxial MEMS accelerometer for low-g applications, along with its fabrication and testing, is reported in this paper. The monolithic structure was optimally designed based on a fully symmetric architecture with a high frequency ratio between the insensitive and the sensitive axes. The sensing substructure was designed, in turn, with a configurable comb-structure for simultaneous biaxial capacitive sensing. This accelerometer was fabricated with high precision and tested under 1-g acceleration, both statically and dynamically. The corresponding static sensitivity is 1.55 μm/g, while the capacitance sensitivity is 113.5 fF/g.

It is first recalled that a Π-joint is a parallelogram four-bar linkage whose coupler link undergoes pure translation w.r.t. its fixed link; moreover, all the points of the coupler link describe circles with identical radii, the length of the other two links. Innovative and sophisticated joints have a crucial role in simplifying the architecture of manipulators for specific tasks, like fast pick-and-place operations. A novel joint is introduced in this paper, dubbed the translating Π-joint, the series array of a prismatic and a Π-joint, the plane of latter being normal to the direction of the former. A realization of the translating Π-joint is the RHRRHR kinematic chain, R and H standing for revolute and screw joint, respectively. Furthermore, four implementations are disclosed here, each with unique features. In addition, the applications of this joint are studied, including two novel architectures for Schonflies-motion generators. The authors report the detailed design and fabrication of two prototypes based on the above-mentioned implementations. The experimental results are used to conduct a comparison between two designs, which reveal their advantages and drawbacks.

The optimum design of a 3- C PS parallel-kinematics machine (PKM), dubbed the SDelta Robot, is investigated in this paper based on a dexterity index. The six-dof PKM described here bears a simple three-limb structure with all its motors mounted on the base, thereby avoiding limb-interference while offering a low inertial load, which makes it quite suitable for high-speed operations. In this paper we find the inverse of the robot forward-kinematics Jacobian matrix symbolically, to be used in singularity analysis, design for isotropy and optimal control; in fact, the inverse derived here applies to all PKMs whose six active-wrench axes intersect pairwise. The inverse of a 6 × 6 matrix is usually difficult to derive or evaluate in symbolic form. We find the symbolic inverse of a Jacobian matrix that is applicable to the large class of PKMs mentioned above, which, to the authors’ knowledge, is an original contribution. Next, we formulate an optimization problem of the robot, based on its condition number, for maximum dexterity. Drawing from the optimization results, we offer some guidelines on choosing the optimum design parameters. It is shown that the SDelta can achieve a local minimum condition number close to unity.

Some studies indicate the potential of multispeed transmissions (MSTs) in improving performance of electric vehicles (EVs), which has led to many developments of MSTs in this context. However, comprehensive dynamics analyses have not been reported yet. For this reason, a mathematical model for MSTs in EVs is being developed, as reported in this paper. This model will be beneficial to support the design and control of EV-oriented MSTs. The transient dynamic response of the transmission is of interest in this study. Therefore, backlash, flexibility, and dissipation of the gear mesh and connecting parts between two planetary gear sets are studied, while taking all these items into account. The system topology variations induced upon gear shifting are given due attention. Simulation results are validated with experiments. The results show that the model can provide a realistic dynamic response of the transmission.

A parallel architecture was recently proposed to generate Schonflies motions. The CRRHHRRC closed kinematic chain offers a symmetric single-loop architecture, isostatic design, and high rotatability 1 of its gripper. This pick-and-place robot uses an innovative cylindrical drive, which is a realization of a two-degree-of-freedom cylindrical actuator. The authors report the kinematics and dynamics analysis of the above-mentioned Schonflies-motion generator, developed at McGill University’s Centre for Intelligent Machines. This analysis is intended to optimize the robot design. Validation of the mathematical model was conducted experimentally. The results reveal the accuracy of the model.

Although electric vehicles (EVs) are more advantageous compared to their internal-combustion-engine (ICE) counterparts, they have failed to gain popularity because of the current state of battery technology. Research demonstrates that an EV equipped with a multi-speed transmission can provide the desired power in more than one way, and therefore, reduce the energy consumption of the vehicle through gear-shifting. However, gear-shifting should be as swift and seamless as possible. We investigate the gear-shifting of a multi-speed transmission for EVs with optimum performance under functional constraints. After deriving the kinematics of the transmission, calculus of variations is employed to find the schedules of the angular velocities during gear-shifting for a swift, seamless operation, which leads to the optimal trajectory in the space of transmission angular velocities. To this end, we resort to polynomial transition functions in the time-domain. After comparing the results obtained with these polynomials, while considering the limitations of the power supply, it is concluded that what we dub the 3-4-5 polynomial offers the optimal performance. The corresponding input torques are also obtained, to guarantee the continuity of the angular velocity, acceleration and jerk. Results show that the proposed approach is highly encouraging for a smooth, swift gear-shifting.

The efficiency of electric vehicles (EVs) should be improved to make them viable, especially in light of the current low energy-storage capacity of electric batteries. Research demonstrates that applying a multi-speed transmission (MST) in an EV can reduce the energy consumption of the vehicle through gear-shifting. However, for effective gear-shifting control in MSTs, first of all, the model of the transmission is required. Moreover, reliable methods should be employed for estimation of the unmeasurable loads and states of the system, under model-based control. This study establishes the mathematical model and estimation algorithms for a novel MST designed for EVs. The main advantages of the designed MST are simplicity and modularity. After devising the dynamics of our proposed transmission, the Kalman filter, the Luenberger obsever and neural networks (NNs) are used to estimate the states, the unknown arbitrary disturbance and the unknown clutch torque applied to the system. Simulation results demonstrate that the proposed approach is suitable for estimation purposes. Experiments were conducted using an in-house prototyped transmission testbed, to validate the simulation results and assess the estimation algorithms.