Experimental analysis of paddling efficiency of elite and non-elite athletes with instrumented canoe sprint C1

Canoeing is an on-water sport admitted by the International Canoe Federation (ICF) and Canoe Sprint became an Olympic discipline in 1936: its programme includes events over 200 m, 500 m and 1000 m. There are numerous Canoe events in single (C1), double (C2) and four (C4) boats. In this discipline the canoeist is kneeling on one knee, and uses a single-bladed flat paddle. In the same way as kayaking, canoeing is a sport whereby propulsion of the boat is derived mainly from muscle actions of the upper body. Conversely, the kneeling position of the canoeist influences the dynamic behaviour of the hull and the force stroke exerted by the single-bladed paddle results in augmented ‘fluctuation’ of the average speed, in greater roll angle and wider pitch span of the canoe with respect to the kayak boat. Besides, the flat shape of the paddle determines the particular paddling technique. In canoeing high forces must be applied at high stroke rates and athletes are coached both in stroke technique and power or resistance training. Elite athletes stand out for the style and efficiency of the stroke, for power and resistance and for skills in the race strategy. Biomechanical measures of canoeing is an important asset to improve performance. In addition comparing results from test to test enables monitoring of an athlete's yearly, and year-to-year improvement. Finally, the experimental analysis of the main kinematical and dynamical parameters allows to examine the shape of the force curves for stroke error detection purposes and to reduce the ineffective hull movements. In this paper the performance and the paddling technique of two elite and two non-elite canoeists are presented by means of an on-water experimental apparatus. Moreover a comparison between the drive phase of the stroke in kayaking and canoeing is proposed. The goals of this research project were to (1) develop a system for on-the-water measurement of paddling performance in kayaking and canoeing, (2) demonstrate the potential of such a system to quantify efficiency and then (3) compare the main kinematical and dynamical parameters of single K1 and C1 boats and the technique differences in paddling style

Vibration Reduction in Robotic Arm Dynamics: Theoretical and Experimental Comparison of Input Shapers

This paper presents the results of a series of experimental tests carried out on the Space Robot Simulator assembly, in order to minimize vibrations of a flexible manipulator for space applications which has been set up at the Department of Structural Mechanics of Università di Pavia, Italy. In particular, the task of the experiments was to test the effectiveness of the command input shaping technique on the vibration reduction, for the open loop control of a flexible manipulator. Input shaping is a method for reducing residual vibrations in high-performance controlled machines. This method requires a simple system model consisting of estimates of the first natural frequencies and damping ratios. Input shaping generates vibration-reducing shaped commands through convolution of a pulse sequence with the desired command. In other words, through the knowledge of the vibrating system, this approach is intended to reduce the final vibration by suitably modifying the actuator inputs. The performance of the input shaper is measured by comparing the residual vibration obtained by the shaped command with the residual vibration obtained by the unshaped command. The aim of this new research is to highlight the effectiveness of the motion input pre-shaping techniques with experimental comparisons between traditionally designed input shapers (IS) and extra-insensitive input shapers (EI), in terms of insensitivity. The technique results in command profiles that are significantly more insensitive to modelling errors or parameter variations than those previously reported. The control technique is verified both with computer simulations and hardware experiments. This work is part of an ASI (Agenzia Spaziale Italiana) multi-objective research project with the aim to design and realize experimental devices for the on orbit validation of control techniques applied to flexible articulated systems

Toward Computerized Determination of Envelope to Family of Parametric Planar Curves

This paper introduces an original analytical procedure for the computation of the planar curve in meshing with a general two dimensional curve. Considering a planar gear mechanism with a constant transmission ratio, in this work a general expression of the explicit solution of the equation of meshing is presented. Besides, an original method to evaluate the undercutting conditions, based on the explicit solution of the equation of meshing, is shown. Taking into account a generating curve in homogeneous coordinates and the transformation matrixes which define the relative motion between the profiles, the solution of the equation of meshing and consequently the profile conjugated to the generating curve can be directly found, by a simple coordinate transformation. The explicit solution is expressed with the general conventions of the theory of gearing. Once the equation of the conjugated curve is obtained, a direct method for the evaluation of the undercutting condition can be applied. The proposed method allows to implement effective and affordable computer codes for the computation of conjugate planar profiles

Theoretical analysis of an original rotary machine

In this study an original analysis of the geometric design of a particular internal pump and an investigation on its theoretical performances are presented. The first part of the work is focused on the geometry of the machine, which is similar to the classical epitrochoidal pumps, but characterized by more complex rotor profiles. Suitable parameters are pointed out in order to completely define the geometry of the machine. In the second part of the paper proper indexes are set and evaluated as functions of the design parameters, in order to evaluate the performance of the machine. The analysis performed allows to highlight the main advantages and drawbacks of this original design in terms of operating performance in comparison with the classical trochoidal pumps

Theoretical Analysis of Internal Lobe Pumps

In this work a theoretical study of the performance of internal epitrochoidal pumps, as a function of the geometrical parameters, is achieved. The machines considered are constituted by two rotors: one rotor has an epitrochoidal profile, and the other rotor is shaped by arcs of circumference and by a limit profile. In this paper the construction of the profiles is performed by the theory of gearing, in order to calculate some selected performance indexes. By choosing three non-dimensional parameters, all the possible geometries of this type of pumps can be examined: in particular, the used approach permits to consider the pump type with epitrochoidal outer rotor too. Finally, a general analysis of the calculated performance and operational indexes is presented

On Twin Screw Compressors Design

Twin screw compressors are widely used in many applications, such as compressing air, refrigerating, industrial gas processing, engines supercharging, etc. In the last quarter of the twentieth century the number of units manufactured registered an extraordinary increase: in fact the development of advanced manufacturing techniques permitted to exploit the basic advantages of these machines in respect to the other types of compressors. In particular twin screw compressors are characterized by the ability to satisfy varying load demands, reliability in service, high efficiency, simple maintenance. Despite the diffusion of this type of machines in many industrial fields, the available literature about them is still limited, in particular regarding the rotor profile geometry. In fact, almost every industrial profile of the rotors is protected by patents, and the companies that hold them seldom diffuse information about the generating methods. In this paper a general description of this type of machine is presented, focusing on the mechanical aspects and in particular on the shape of the rotors. The first part of the paper introduces the main advantages and disadvantages in respect to the other compressor types and the state of the art of this type of machine. Then a deep mathematical analysis of a method for the profiling of screw compressor rotors, based on the theory of gearing, and typical aspects related to the machine design, such as the rotor flow area, the sealing line on the cross-sectional plane and on the rotors and the blow-hole area, are discussed. In the second part of the work the theory above presented is applied to three different geometries of the rotors, and other possible more complex profiles are introduced

Theoretical Analysis of Internal Epitrochoidal and Hypotrochoidal Machines

In this article, a complete and original method to analyse both the epitrochoidal and the hypotrochoidal rotary machines is presented. The internal trochoidal machines consist of two rotors: the first rotor is an envelope of a trochoid, the second rotor is its conjugate. In particular, in this article, the profiles of the trochoidal rotor and its conjugate are expressed by original and particularly synthetic equations using a method based on the theory of gearing. Then the geometry of these machines is completely defined by the choice of four non-dimensional parameters. Once these parameters are selected, the geometric and kinematic characteristics of the rotor profiles are obtained in an original analytic form; hence, the main theoretical performance indexes are computed by a proper method. The results of the analysis allow us to choose the best geometric configuration for a specific application

Lateral Force Components on Pedals measured by a Cycle Ergometer with Three Axial Load Cells

This paper is focused on the measurements and analysis of the three components of the force on pedals in bicycling through a special cycle-ergometer prototype [4]. This machine allows to study the kinematics and dynamics of the bycicle-riders by quantitative measurements. The pedals are equipped with a three-axial load cells measuring the pedalling force in three orthogonal directions, and with two encoders measuring the angular positions of foots. A third encoder is mounted on the central movement, for the measurement of the crank rotation angle. The ergometer, developed for cycling sport performances and for clinical analysis, allows to measure the lateral components on the pedals, perpendicular to the para-sagittal plane. Notwithstanding the literature usually neglects the lateral components in non pathological subjects, they represent meaningful informations in rehabilitation treatment of pathological subjects. Moreover the biomechanical analysis of pedalling through three-axial force measurements allows to improve efficiency during cycling sports

Evaluation of Paddling Performances through Force Acquisitions with a Specially Instrumented Kayak

Kayaking is an athletic discipline admitted by the International Canoe Federation (ICF). In flat-water racing events, paddlers race on a straight course, each boat in a separate lane, over different distances up to 1000 m. There are kayak events, for men and women, in single (K1), double (K2) and four paddlers (K4). This form of racing is an Olympic discipline and its programme includes events over the distance of 500 m and 1000 m. Unlike canoeing, where the paddler is kneeling on one knee, and uses a single blade paddle, the kayak athlete is seated and uses a two-blade paddle. Both kayaking and canoeing are sports whereby propulsion of the boat is derived mainly from muscle actions of the upper body. This paper presents the evaluation of paddling athletic performances during K1 training session by means of an instrumented kayak with a stand-alone data acquisition system. The on purpose experimental device is first presented. Force strokes measured through instrumented paddle with strain gauges at both ends are simultaneously recorded with the hull speed of the boat. A deep analysis of the different phases of the stroke sequence (i.e. 1-preparation and catch phase, 2-propulsion power or stroke, 3-stroke end 4-exit phase and aerial preparation of the next stroke) is available for each training session of the athlete. Effect of stroke rate on average velocity and on the application and exertion of force during the drive phase of the stroke cycle is analyzed. In this way some important considerations can be related to paddling parameters such as the angular offset of the blades, the grip width and the angle of attack which is the angle at which the blade enters the water. Quantitative measurements of paddle forces during on-water training offer a particularly suitable system to evaluate the techniques of paddling and racing sprint boats and to refine the efficiency of stroke and paddling style