Portable instrumented resistance swimming device with magnetic particle brake

Abstract

A portable, instrumented, resisted swimming device with a magnetic particle brake, characterized in that it comprises: a support structure (6) with an anchor plate (3) and an adjustable fixing system for attaching it to a ledge or pool edge; an inextensible rope; a storage reel (10) arranged for storing the rope; a retrieval motor (7) mechanically coupled to the storage reel (10); a brake reel or traction pulley (12) separate from the storage reel (10), of substantially constant radius, around which the rope is wound at least once; a magnetic particle brake (8) coupled to the shaft of the brake reel or traction pulley (12); a force cell (4) based on a strain gauge arranged for measuring the tension of the rope or a structural reaction of the support structure (6); an encoder (13) coupled to the brake reel or traction pulley (12); a rope guide (9) arranged in the rope's exit path; and an electronic unit housed in a compartment (1) and electrically connected to the brake (8), the motor (7), the force cell (4), and the encoder (13).

Description

Portable instrumented resistance swimming device with magnetic particle brake TECHNICAL SECTOR The present invention falls within the technical field of physical performance assessment equipment and sports ergometry applied to aquatic sports. More specifically, it relates to a portable resisted swimming device designed to record force, speed, and pulling power during pool exercises, especially in fin swimming and lifesaving and rescue tests (e.g., manikin tow). BACKGROUND OF THE INVENTION In the field of pool training and assessment, several methods are used to introduce resistance and / or measure an athlete's effort: i) fixed-belt tests, which provide primarily static or quasi-static information; ii) elastic bands, whose resistance varies with elongation; and iii) tower systems with pulleys and weights, which can approximate a constant load but are usually bulky, slow to set up, and not very portable. Solutions also exist using cable wound on a reel with associated braking and sensor systems. Within this latter group, the Spanish utility model ES 1272 289 U is particularly relevant due to its proximity, which discloses a device for evaluation and training in swimming by means of a thread or rope wound on a reel, where on the same axis braking means and / or motor means act and rotation sensors and an electronic control unit are associated. In these systems, since the braking and sensors act on the same storage drum, the effective winding radius varies during unwinding / winding. Therefore, even when the braking torque is approximately constant, the force transmitted to the user varies with the length of rope deployed, reducing load consistency and comparability between tests, especially on typical long runs of 25 to 50 m. Also known is US patent 5,391,080, relating to a swimming instruction, training, and evaluation apparatus, in which a rope is wound around a drum driven by a variable-speed motor, and positive and negative forces are applied to the swimmer by electronically controlled electrodynamic means. In this solution, the generation of charge depends on the motorized system associated with the drum and its control. Although these solutions provide useful instrumentation, they do not fully resolve the need for a highly portable and readily mountable device that provides substantially constant tensile strength independent of the variable radius of the storage reel, uses a brake with high metrological stability in a dedicated constant-radius organ, and also incorporates rope angle correction to compensate for user depth variations, along with calibration routines and protection against the aquatic environment. Therefore, there is a technical need for a device that can be easily attached to a bench or equivalent surfaces, capable of providing a substantially constant and reproducible tensile strength, and which simultaneously allows for highly accurate measurement of force and speed (and therefore power) during pool exercises, especially in fin swimming and mannequin towing in lifesaving and rescue. EXPLANATION OF THE INVENTION In aquatic rope training systems, the applied resistance and the measurement of kinematic and dynamic variables can be affected by variations in the winding radius, the geometric dependence of the rope's trajectory on the athlete's position, and the limited metrological repeatability under real pool conditions. The present invention overcomes these drawbacks with a highly portable device, anchorable to a bench or equivalent surfaces, that functionally decouples rope storage and load generation: a first drum stores and retrieves the rope with reduced friction, assisted by a motor for rewinding, while a second drum or pulley, with a substantially constant radius, acts as the braking and measuring element, around which the rope is wound at least once to ensure stable, slip-free transmission.A magnetic particle brake, controlled by an electronic unit, acts on this component, allowing for highly stable load and / or power profiles. It incorporates thermal compensation and force and speed calibration routines. The system includes a load cell to measure rope tension and an encoder to measure the angular velocity of the braking drum. Power is calculated via the F·vy pathway and, additionally, via the · pathway, based on the controlled brake torque, improving traceability and consistency of the results. Furthermore, a rope angle sensor allows for real-time correction of the measured values ​​based on the athlete's underwater position, providing a more representative estimate of the effective effort component.This results in a compact, repeatable, and highly accurate device for capturing force, speed, and power curves, and for reliably evaluating specific fin work in the pool under operating conditions. MAIN ADVANTAGES The proposed architecture offers, among others, the following technical advantages: i) load consistency when the brake is disengaged from the storage reel; ii) high reproducibility due to the use of a magnetic particle brake and direct measurement of force and speed at the brake mechanism; iii) portability and absence of bulky pulley and weight systems; iv) automated rope retrieval by motor; v) generation of advanced biomechanical information (intracycle curves and parameters) useful for finning and towing techniques; vi) robustness in aquatic environments thanks to watertight sealing and IP protection rating; vii) possibility of guided force and speed calibration; and viii) metrological improvement through correction of the rope angle relative to the water plane. BRIEF DESCRIPTION OF THE DRAWINGS To complement the description being made and to help in a better understanding of the characteristics of the invention, a set of drawings is included in which, for illustrative and non-limiting purposes, the following has been represented: Figure 1.- Shows a schematic side view of the device. Figure 2.- Shows a perspective view of the device. The following reference symbols have been used in these figures: 1 Plate compartment; 2 Data cable; 3 Anchor plate; 4 Force cell; 5 Wiring box; 6 Support structure; 7 Take-up motor; 8 Magnetic particle brake; 9 Rope guide (with integrated angle sensor); 10 Storage reel; 11 Take-up pulley; 12 Brake reel; 13 Encoder. PREFERRED EMBODIMENT OF THE INVENTION In a preferred embodiment, the device comprises a water-resistant housing or support structure (6), for example, made of anodized aluminum, stainless steel, or engineering plastic. The structure (6) incorporates an anchor plate (3) and an adjustable fixing system (for example, clamps or jaws) for quick and secure mounting on a starting block or the edge of the pool, maintaining a reproducible rope exit geometry. Preferably, the housing incorporates watertight gaskets, covers, and through-wall fittings to achieve an IP65 or higher protection rating and protect the electronics from moisture and splashes. Inside the structure (6) is a storage reel (10) connected to a rewind motor (7). This reel (10) is designed to rotate with reduced friction during use (i.e., without being subjected to significant braking torque) so that its variable radius due to winding does not affect the load applied to the user. The motor (7) preferentially operates in rewind mode at the end of the test, with the brake (8) deactivated or reduced, to automatically retrieve the rope. The resistance to the user's forward motion is generated by a brake reel or traction pulley (12) separate from the storage reel (10). The inextensible rope is guided by the rope guide (9) and wrapped around the brake reel (12) at least one complete turn (preferably one or more turns), so that the transmitted tension is mechanically coupled to the shaft of the reel (12). A brake (8), preferably a magnetic particle brake, adjustable by excitation current and capable of providing a stable and repeatable torque, is coupled to the shaft of the brake reel (12). Since the effective radius of the brake reel (12) remains substantially constant, the resistive force perceived by the user is essentially constant for a given braking torque. For force measurement, the device incorporates a strain gauge-based force cell (4) arranged to measure rope tension or the structural reaction associated with the brake reel (12). In one particular embodiment, the force cell (4) is located between the anchor plate (3) and the support structure (6), forming part of the resistant mechanical path between the pool edge or coping and the device housing, as shown in Figure 1. In another particular embodiment, the force cell (4) is located on a support mechanically linked to the brake reel (12), with this support receiving a reaction proportional to the rope tension. For displacement and velocity measurement, the device incorporates an encoder (13) coaxially coupled to the brake reel (12) or its shaft, thus enabling high-resolution measurement of the rope's linear velocity. In a preferred embodiment, the rope guide (9) integrates an angle sensor configured to measure in real time the orientation of the rope section towards the user, both in vertical and lateral components, so that the system can geometrically correct the measured magnitudes when the user moves under the device, submerges or modifies its depth during the test. The winding motor (7) is coupled to the storage reel (10) by means of a mechanical winding transmission independent of the brake reel shaft (12), so that the motor's action on the reel (10) does not interfere with the braking and measuring mechanism. Furthermore, the storage reel (10) is mounted with a rotational resistance significantly lower than the resistance generated by the brake (8) on the brake reel (12), and it lacks active braking elements, so its variable radius due to winding does not affect the load applied to the user. The rope wraps around the brake reel (12) one or more full turns, establishing an adhesive contact with the reel or pulley, so that tension is transmitted to the reel shaft (12) without slippage under normal operating loads. To improve this contact, the brake reel (12) may include an adhesive coating, a groove adapted to the rope diameter, or both. The magnetic particle brake (8) is electrically connected to an excitation current controller, which may be integrated into or connected to the electronic unit. The encoder (13) is coaxially coupled to the shaft of the brake spool (12), so that the rotation of the spool is associated with an electrical angular position signal. Additionally, the device can perform integrated characterization and calibration routines: i) force calibration by applying reference loads to adjust the sensitivity and zero of the force cell (4); ii) speed and displacement calibration by verifying the encoder (13) on the brake reel (12) and, where appropriate, adjusting the effective radius of the reel (12) to convert angular speed into linear speed; iii) characterization of the torque of the magnetic particle brake (8) by obtaining a torque curve as a function of the excitation current and temperature, storing a current-torque conversion map for use during testing; and iv) periodic verification of metrological consistency by comparing the power estimated by force and speed with the power estimated by torque and angular speed. An electronic board housed in compartment (1) simultaneously acquires the signal from the force cell (4) and the encoder (13), and generates: i) the excitation current required for the magnetic particle brake (8) according to a selected setpoint (e.g., approximately constant target force), and ii) the activation commands for the retrieval motor (7) to recover the rope at the end of the stroke. The data is transmitted to a computer via the data cable (2) or other communication means, such as a wireless communication module, where dedicated software displays and stores the force, velocity, and power (force-velocity product) curves and allows for specific analysis of the technical movements in fin swimming and pool tows. In a preferred embodiment, the electronic unit is configured to estimate the torque applied by the brake (8) from the current-torque conversion map and, optionally, from a temperature measurement of the brake assembly, calculating a mechanical power at the shaft as the product of the estimated torque and the angular velocity measured by the encoder (13). Simultaneously, the system calculates the power from the force measured by the load cell (4) and the linear velocity of the rope, and can record both power curves to improve measurement traceability and quantify internal system losses. Likewise, the brake control (8) can operate in different modes: i) approximately constant force mode (target voltage), and ii) approximately constant power mode or programmable power profile mode, in which the electronic unit adjusts the brake current to maintain a target power based on the measured speed, allowing incremental, stepped or interval protocols with high repeatability in the pool. Angular correction (9) can be applied not only to force and speed, but also to the useful power in the forward direction, calculating projected components using trigonometric functions in real time. This provides a more representative estimate of the effective work performed by the user when there are changes in depth or alignment with respect to the device. In a preferred embodiment, the associated software calculates test quality and technique indicators, such as the temporal stability of force and / or power (e.g., coefficient of variation in time windows), string angle stability, and the relationship between power at the brake axis and corrected useful power. These indicators allow for standardization of the test and comparison of sessions or athletes based on objective criteria. Before each session or repetition, the system can perform an automatic self-check by applying known current levels to the brake (8) for a brief period without active user input and / or with the rope at rest. This verifies the correct operation of the sensors, communications, and basic consistency of the measured values. In case of deviations outside of tolerance, the software can alert the operator and record the event. In a preferred embodiment, the device further comprises a temperature sensor associated with the magnetic particle brake (8), the electronic unit being configured to compensate for torque estimation and / or brake control based on the measured temperature. As auxiliary elements, the device may include a retrieval pulley (11) and / or additional guides that ensure smooth rope movement, minimize parasitic friction, and prevent accidental slippage. The rope guide (9) and / or the retrieval pulley (11) are located inside the support structure (6), defining the rope's path. Furthermore, the anchoring system may incorporate anti-slip elements and adjustable clamps, jaws, or pressure elements with adjustable opening and / or height to adapt to ledges or pool edges of varying shapes. INDUSTRIAL APPLICATION The invention is suitable for industrial application in the manufacture of sports training and assessment equipment. It can be produced by instrumentation companies, machining workshops, and sports equipment manufacturers, and used in high-performance centers, clubs, federations, universities, and biomechanics laboratories, especially for 25-30 m fin swimming and manikin towing tests in a pool, as well as for training assessment and monitoring programs.

Claims

1. A portable, instrumented, resisted swimming device with a magnetic particle brake, characterized in that it comprises: a support structure (6) with an anchor plate (3) and an adjustable fixing system for attaching it to a ledge or pool edge; a non-extensible rope; a storage reel (10) arranged for storing the rope; a retrieval motor (7) mechanically coupled to the storage reel (10); a brake reel or traction pulley (12) separate from the storage reel (10), of substantially constant radius,around which the rope is wound at least one complete turn; a magnetic particle brake (8) coupled to the shaft of the brake reel or traction pulley (12); a force cell (4) based on a strain gauge arranged to measure rope tension or a structural reaction of the support structure (6); an encoder (13) coupled to the brake reel or traction pulley (12); a rope guide (9) arranged in the rope's exit path; and an electronic unit housed in a compartment (1) and electrically connected to the brake (8), the motor (7), the force cell (4), and the encoder (13).

2. Device according to claim 1, characterized in that the storage reel (10) is mounted with a resistance to rotation substantially lower than the resistance generated by the brake (8) on the brake reel or traction pulley (12), and lacks active braking elements.

3. Device according to any of the preceding claims,characterized in that the retrieval motor (7) is coupled to the storage reel (10) by means of a mechanical transmission independent of the shaft of the brake reel or traction pulley (12).

4. Device according to any of the preceding claims, characterized in that the rope wraps around the brake reel or traction pulley (12) one or more complete turns, in adherent contact with said reel or pulley (12).

5. Device according to any of the preceding claims, characterized in that the brake reel or traction pulley (12) includes an adherent coating, a groove adapted to the diameter of the rope, or both.

6. Device according to any of the preceding claims, characterized in that the magnetic particle brake (8) is connected to an excitation current controller integrated into or connected to the electronic unit.

7. Device according to any of the preceding claims,characterized in that the encoder (13) is coaxially coupled to the shaft of the brake reel or traction pulley (12).

8. Device according to any of the preceding claims, characterized in that the force cell (4) is located between the anchor plate (3) and the support structure (6), forming part of the resistant mechanical path between the pool edge or coping and the device housing.

9. Device according to any of claims 1 to 7, characterized in that the force cell (4) is located on a support mechanically linked to the brake reel or traction pulley (12).

10. Device according to any of the preceding claims, characterized in that the rope guide (9) integrates an angle sensor comprising at least one of the following elements: an inclinometer, an inertial sensor, an optical sensor, or a roller assembly with position measurement.

11. Device according to any of the preceding claims,characterized in that it comprises a rope guide (9) and / or a retrieval pulley (11) arranged inside the support structure (6) to define the rope path.

12. Device according to any of the preceding claims, characterized in that the adjustable fastening system comprises jaws, clamps, or pressure elements adjustable in opening and / or height.

13. Device according to any of the preceding claims, characterized in that the electronic unit includes communication means, comprising at least one data cable (2) or a wireless communication module.

14. Device according to any of the preceding claims, characterized in that the assembly is housed in a compact, transportable casing provided with watertight seals, covers, or through-holes, and does not require external weight and pulley systems to generate resistance.

15. Device according to any of the preceding claims,characterized in that it comprises a temperature sensor associated with the magnetic particle brake (8).,