Improving bulldozer productivity through adaptive control of traction and working modes

Abstract

The growing share of earthmoving performed on soils of high excavation difficulty runs into a limitation that cannot be removed by increasing installed power. With the adhesion weight fixed, any increment of drawbar pull beyond the realizable adhesion threshold is converted into track slip, and the useful share of engine power decreases faster than the pull grows. The gap between design and actual output persists both with a sound transmission and with an experienced operator. The purpose of the work is a quantitative estimate of the productivity reserve opened by joint regulation of the traction and speed mode together with blade depth following the slip signal. An author's simulation model of the working cycle of a tracked bulldozer with an operating mass of 21,4 t and a hydromechanical transmission has been built; the calculation runs with a 0,02 s step for three control strategies, three soil groups and push distances of 20-80 m. The maximum tractive efficiency is reached at an adhesion weight utilization factor of 0,553 and a slip of 0,146. The baseline strategy keeps the machine at a mean slip of 0,292, that is, well to the right of the optimum. Joint regulation shortens the cycle from 88,5 to 80,1 s and raises technical productivity by 12,1% while specific fuel consumption falls by 6,0%; on group III soils the gain reaches 23,4%. The elasticity of productivity with respect to the adhesion coefficient drops from 0,288 to 0,089. A control loop driven by slip moves the bulldozer from a mode in which output follows the soil condition into a mode in which output is held almost independently of it.