Structure testing machine

A structure testing machine for carrying out tests on a test structure for an assessment of the response of the structure to test loads applied to the structure in the direction of a predetermined axis of the structure under the control of a monitored control system which forms part of the machine and which has a forward path which includes an actuator which is supported by a machine frame and which upon actuation applies to the test structure a test load in the direction of the predetermined axis, and a controller responsive to a controller input signal and to controller parameters to apply to the actuator an actuating signal to cause the actuator to subject the test structure to a test load which produces dimensional changes in the test structure in the direction of the predetermined axis, characterized by the provision of an adaptive control loop which comprises a stiffness estimator which generates from the dimensional changes in the test structure adaptive control signals representative of the structure stiffness and adaptive control signals representative of the combined stiffness of the actuator, actuator support frame and the test structure, and means to update the controller parameters of the controller to modify the forward path gain of the controller in response to the adaptive control signals thereby to adapt the machine to changes in the stiffness of the test structure relative to the combined stiffness of the machine and the test structure, the monitored control system being a closed loop system which includes a feedback path for feeding back condition signals representative of a predetermined condition of the test structure a result of the application of a control input signal to the controller and comparison means responsive to an input demand signal and the condition signal to generate a controller input signal representative of the difference between the input demand signal and the condition signal, and the adaptive control loop including a machine model which provides a mathematical representation of the machine and which generates machine model parameters, and a controller design responsive to test specification inputs applied thereto and representative of predetermined alternative tests to modify the model parameters and to generate updating controller parameters.

A structure testing machine for carrying out tests on a test structure for an assessment of the response of the structure to amplitude varying test loads of high frequency applied to the structure in the direction of a predetermined axis of the structure under the control of a monitored control system which forms part of the machine and which has a forward path which includes an actuator which is supported by a machine frame and which upon actuation applies to the test structure a test load in the direction of the predetermined axis, and a controller responsive to a controller input signal and to controller parameters to apply to the actuator an actuating signal to cause the actuator to subject the test structure to a test load which produces dimensional changes in the test structure in the direction of the predetermined axis, characterized by the provision of an adaptive control loop which comprises a stiffness estimator which generates from the dimensional changes in the test structure adaptive control signals representative of the structure stiffness and adaptive control signals representative of the combined stiffness of the actuator, actuator support frame and the test structure, and means to update the controller parameters of the controller to modify the forward path gain of the controller in response to the adaptive control signals thereby to adapt the machine to changes in the stiffness of the test structure relative to the combined stiffness of the machine and the test structure, the machine further comprising means to store measured stiffness values together with their corresponding time or position or load or strain values and to make a predictive correction to the adaptive control signals generated by the stiffness estimator to compensate for the delay in the response of the estimator and the machine to changes in test structure stiffness during subsequent test load cycles.