Development of a Prototype Dynamic Weighing System for Single Bucket Excavator

Some earthmoving works performed by single bucket excavators require on-line weighing of material transported by excavator's bucket. Such measurements are critical e.g. for optimal loading of dump trucks. The first commercially available payload weighing systems for single bucket excavators were called static systems. To properly estimate bucket load, the machine equipped with them had to be kept in a standstill condition for a few seconds. Consequently, productivity of the machine was low. Recently dynamic weighing systems have been introduced. These systems enable to precisely weigh the material collected in the bucket while swinging excavator's house as well as moving its boom, arm or bucket. Thus, they do not influence productivity of the machine. Such systems are commercially available nowadays. Development of reliable dynamic weighing systems requires certain problems to be resolved. Firstly, the influence of acceleration acting on excavator's bodies and bucket payload has to be taken into account. Values of pressure inside cylinders supporting excavator's boom, which are usually used as input signals for payload mass computation, significantly differ in dynamic and static conditions. In order to provide satisfactory weighing performance, internal friction of hydraulic cylinders cannot be also omitted. A prototype dynamic weighing system for single bucket excavator developed in The Department of Off-Road Machine and Vehicle Engineering (Wroclaw University of Science and Technology) will be presented in the article. While estimating bucket payload the system allows for acceleration acting on excavator bodies as well as hydraulic cylinders friction.