A. De Carli

A fuzzy-PI control strategy☆

Abstract Fuzzy logic is used to attain the on-line adaptation of the parameter values for a proportional and integral control strategy. The design procedure of the fuzzy logic algorithm is firstly shown. Subsequently it is applied to a simulated system representative of a realistic controlled plant. A set of validation tests conclude the paper.

Safety of third-generation artificial turf in male elite professional soccer players in Italian major league

Our hypothesis is that there are no difference in the injury incidence on artificial turf and natural grass. During the 2011/2012 season, we recorded injuries which occurred to two Italian stadiums equipped with third‐generation artificial turf during 36 games (391 players). Data were compared with the injuries which occurred in the same season in two stadiums equipped with natural grass (372 players). We recorded 43 injuries during the playing time (16.7 per 1000 h). About 23 (18.1 per 1000 h) injuries occurred on artificial turf, while 20 (15.2 per 1000 h) on the natural grass with no statistical differences P > 0.05. We recorded 10 (7.87 per 1000 h) contact and 13 (10.23 per 1000 h) non‐contact injuries on artificial turf, while 5 (3.8 per 1000 h) contact and 15 (11.4 per 1000 h) non‐contact injuries on natural grass P > 0.05. The overall relative risk was 1.15; 95% CI: 0.64–2.07). Our study demonstrates a substantial equivalence in injury risk on natural grass and artificial turf in elite professional soccer athletes during official matches.

A comparison of some control strategies for motion control

Abstract Fast dynamics and high accuracy are the main performance requirements in motion control applications. Their attainment implies not only advanced technology in actuators and instrumentation, but also innovative control strategies. The most significant ones are applied to a highly nonlinear mechanical system in order to obtain a comparative qualification.

A robust control strategy for an unstable mechanical system

The unstable mechanical system used to test the robust control strategy is a beam and ball system. The main nonlinearities are due to stiction and friction in the servomotor which moves the beam, the main uncertainties are due to the ball size variations. The beam position is perturbed by external disturbances acting on the beam. The proposed robust control strategy compensates the static friction by acting on the supply voltage of the motor, makes the behavior of the beam almost independent of the ball size variation, makes the system behavior insensible to external disturbance by the online compensation of their estimated value. Simulation and experimental tests confirm the validity of this approach.

Motion control: An emergent technology

Abstract The most relevant aspects in designing a device for the control of a mechanical system are outlined. The peculiarities in the modelling of the load are first indicated. Subsequently, the features of the converter motor unit used for generating the torque are examined. Finally, the characteristics of the control strategies are indicated, along with the differences between the most commonly used ones.

Can an adjustable-loop length suspensory fixation device reduce femoral tunnel enlargement in anterior cruciate ligament reconstruction? A prospective computer tomography study

BACKGROUND The aim of this study was to compare bone femoral tunnel enlargement in patients who underwent anterior cruciate ligament (ACL) transtibial reconstruction using an adjustable-loop length suspensory fixation device and a fixed-loop length suspensory fixation device. METHODS All patients treated for ACL reconstruction with an ipsilateral hamstring between March 2013 and March 2014 were evaluated. Subjects were assigned to Group A (TightRope™ (TR) femoral fixation) or Group B (EndoButton® (EB) femoral fixation). All patients were evaluated with the Lachman test, pivot-shift test, 2000 International Knee Documentation Committee (IKDC) knee examination and KT1000 arthrometer. The subjective evaluation was performed using the 2000 IKDC Subjective Knee score, the Lysholm knee score, and the Tegner activity scale. CT examination was performed to evaluate femoral tunnel enlargement at four different levels. All patients were assessed at a 12month follow-up visit. Power analysis was performed a priori in accordance with the femoral tunnel enlargement values from the CT scans. Differences with P-values of ≤0.05 were considered to be statistically significant. RESULTS The groups were homogenous at baseline with regard to age, gender, BMI, dominance and disease duration. At the final follow-up, no statistically significant differences (P>0.05) were found according to subjective and objective clinical outcome measures. According to the femoral tunnel enlargement, no statistically significant difference was found between the two groups (P>0.05). CONCLUSION In transtibial ACL reconstruction, the use of a fixed or adjustable-loop length device products, on the femoral side, led to similar clinical and radiological results.

How four and twelve weeks of implantation affect the strength and stiffness of a tendon graft securely fixed in a bone tunnel: a study of Evolgate fixation in an extra-articular model ovine model

Healing of a tendon graft to a bone tunnel is slower than the healing of a bone plug. Therefore, the device chosen for hamstring fixation may need to maintain its strength and stiffness longer than the device chosen for bone-tendon-bone fixation. We evaluated, in an extraarticular ovine model, how 4 and 12 weeks of implantation affect the strength of a tendon graft fixed to bone with the Evolgate. The long digital extensor tendon was transplanted and fixed with the Evolgate into a 30-mm long, 8 mm diameter bone tunnel drilled in the tibial metaphysis of both posterior limbs of 15 skeletally mature Suffolk sheep. Immediately after implantation, and 4 and 12 weeks later, biomechanical cyclic load tests in 50 N increments were performed until failure to evaluate the ultimate failure load (UFL). Histological analysis was also performed at 4 and 12 weeks. Biomechanical tests revealed a UFL of 339±120 N at time 0, and increases to 635±19 N (4 weeks) and to 867±80 N (12 weeks). The differences between all 3 groups were significant (p<0.001, paired t test). The histological evaluation showed a layer of cellular, fibrous tissue between the tendon and the bone, along the length of the bone tunnel; this layer progressively matured and reorganized during the healing process. The collagen fibers that attached the tendon to the bone resembled Sharpey’s fibers. The strength of the interface significantly and progressively increased between weeks 4 and 12 after transplantation, and was associated with a degree of bone ingrowth noted histologically. The use of the Evolgate seems not to interfere with the bone ingrowth after implantation, allowing an improvement in strength of the bonetendon- device complex.

Revision ACL reconstruction using doubled semitendinosus and gracilis tendons: a follow-up study

Few papers report the results of revision ACL reconstruction with hamstrings tendons. We report our results with revision anterior cruciate ligament (ACL) surgery using a doubled gracilis and semitendinosus tendons (DGST) graft, in association with an exta-articular procedure. Twelve patients underwent ACL revision surgery using autogenous homolateral DGST graft in association with an extra-articular procedure and were evaluated at a mean follow-up of 35 months. At follow-up evaluation, all patients scored negatively on the Lachman test and normally or near normally on the jerk test. The KT 1000 evaluation showed a average side-to-side difference at 30 lb and MM of 1.4±1.7 mm and 1.6±1.6 mm, respectively. The Lysholm score was 98±2 (range, 94–100); excellent results (score 95–100) were obtained in 83% of cases, good results (score 84–94) in 17%, and no fair or poor results. At the IKDC evaluation, the result was excellent (normal) in one-thirds of cases and good (nearly normal) in twothirds. Therefore, the use of hamstring tendons in association with lateral tenodesis seems to be a good alternative to the use of allografts or contralateral bone-patellar tendon-bone graft in revision ACL reconstructions.

A Benchmark Example to Qualify a Control Strategy for Motion Control

The control of mechanical motion has importance in industrial automation. In discrete event production systems, the quality of the motion determines plant productivity, product quality, energy saving and implementation efficiency. In continuous production systems, the control of mechanical motion improves the performances of pumps, compressors, valves etc. Control of mechanical motion is applied to isolated devices or interacting mechanisms. The rated power ranges between less then one watt to many kW.

Anterolateral ligament reconstruction with autologous grafting: A biomechanical study.

Background To evaluate the reliability of the Iliotibial band compared to gracilis tendon as a graft to be used in anterolateral ligament reconstruction. Methods Gracilis tendon and a strip of Iliotibial band compared were harvested from 8 fresh human cadaveric knees. The gracilis tendon was prepared to obtain a graft of 10 cm in length (Group 1). Iliotibial band compared was prepared to obtain a graft of 10 cm in length and 0.5 cm in width from the middle portion (Group 2). All the specimens were fixed on a servo hydraulic tensile machine with dedicated cryo‐clamp. The loading protocol, used to compare the previously published results of ultimate failure load and Stiffness of the anterolateral ligament (Group 3), included a cyclic preconditioning between 10 and 25 N at 0.1 Hz for 10 cycles and then a load to failure test at 20 mm/min. Findings Gracilis tendon showed higher Ultimante Failure Load and stiffness when compared to a strip of Iliotibial band. Gracilis tendon and a strip of Iliotibial band compared showed higher Ultimante Failure Load and stiffness when compared with native anterolateral ligament as reported by Kennedy. Interpretation Both grafts tested in the present studies are suitable for an anatomical anterolateral ligament reconstruction. HighlightsGracilis and Iliotibial‐band are the most used graft for the ALL reconstruction.Gracilis and Iliotibial‐band showed higher UFl than native ALL.Gracilis and Iliotibial‐band showed higher stiffness than native ALL.Gracilis and Iliotibial‐band are suitable graft for ALL reconstruction.