Abstract: A variable stiffness joint and method to alter the stiffness of the joint with multiple stiffness levels is described wherein a plurality of stiffness bits (m) are used for enabling 2 m stiffness level variations for the joint. Each stiffness bit comprises an elastic element in mechanical connection with a clutch (21, 22, 23). The joint revolves with zero stiffness level when all the clutches (21, 22, 23) are disengaged whereas a clutch (21, 22, 23) involves one of the elastic elements which alter the stiffness of the joint. Engaging other clutches (21, 22, 23) involve more elastic elements for altering the joint stiffness and the resultant joint stiffness is determined by adding the stiffness values of all the involved springs (6, 7, 8).

Abstract: A variable stiffness joint and method to alter the stiffness of the joint with multiple stiffness levels is described wherein a plurality of stiffness bits (m) are used for enabling 2 m stiffness level variations for the joint. Each stiffness bit comprises an elastic element in mechanical connection with a clutch (21, 22, 23). The joint revolves with zero stiffness level when all the clutches (21, 22, 23) are disengaged whereas a clutch (21, 22, 23) involves one of the elastic elements which alter the stiffness of the joint. Engaging other clutches (21, 22, 23) involve more elastic elements for altering the joint stiffness and the resultant joint stiffness is determined by adding the stiffness values of all the involved springs (6, 7, 8).

Abstract: The present invention introduces a new concept of applying a parallel mechanism in automated fiber placement for aerospace part manufacturing. The proposed system requirements are 4DOF parallel mechanism consisting of two RPS and two UPS limbs with two rotational and two translational motions. Both inverse and forward kinematics models are obtained and solved analytically. Based on the overall Jacobian matrix in screw theory, singularity loci are presented and the singularity-free workspace is correspondingly illustrated. To maximize the singularity-free workspace, locations of the two UPS limbs with the platform and base sizes are used in the optimization which gives a new design of a 4DOF parallel mechanism. A dimensionless Jacobian matrix is also defined and its condition number is used for optimizing the kinematics performance in the optimization process. A numerical example is presented with physical constraint considerations of a test bed design for automated fiber placement.

Abstract: The present invention introduces a new concept of applying a parallel mechanism in automated fiber placement for aerospace part manufacturing. The proposed system requirements are 4DOF parallel mechanism consisting of two RPS and two UPS limbs with two rotational and two translational motions. Both inverse and forward kinematics models are obtained and solved analytically. Based on the overall Jacobian matrix in screw theory, singularity loci are presented and the singularity-free workspace is correspondingly illustrated. To maximize the singularity-free workspace, locations of the two UPS limbs with the platform and base sizes are used in the optimization which gives a new design of a 4DOF parallel mechanism. A dimensionless Jacobian matrix is also defined and its condition number is used for optimizing the kinematics performance in the optimization process. A numerical example is presented with physical constraint considerations of a test bed design for automated fiber placement.

Abstract: A sensor is described for detecting the force applied to or by soft material, and that is thus able to measure the stiffness of a soft material. The sensor comprises a sensor body into which is supplied a fluid under pressure. At least one sensor members are provided that are arranged to project from the sensor body under the pressure exerted thereon by the fluid. A sensor member displacement detection system is also provided, that is preferably optically based using optical fibres to illuminate the sensor member and that measures the modulation of the light reflected from the sensor member as the member is displaced against the pressure of the fluid to detect and measure the displacement. From the measured displacement an estimate of the force being applied to the sensor member can be obtained. The sensor is of a small size suitable for use during MIS or catheterisation procedures. Preferably the sensor is constructed of non-metallic material such that it is MRI compatible.