Redundancy-enabled stabilisation of linear encoder performance: The biSLIDER

Linear encoders are widely used in industry particularly for machine tools. Their performance may suffer thermal and mechanical instability. This paper presents a technique to stabilise the performance over time by recovering to a reference state. It is based on the simultaneous readings of two heads separated by an invariant spacer. It requires off-the-shelf components only and is widely applicable in industry. Experimental results in the field and in lab show excellent error recovery even in the presence of highly nonlinear errors.