Automated soil hardness testing machine

This paper describes the design and performance of a mechatronic system for controlling a standard drop-hammer mechanism that is commonly used in performing outdoor soil or ground hardness tests. A low-cost microcontroller is used to control a hydraulic actuator to repeatedly lift and drop a standard free-falling weight that strikes a pipe (sampler) which is pushed deeper into the ground with each impact. The depth of the sampler pipe and position of the hydraulic cylinder are monitored and the number of drops, soil penetration depth and other test information are recorded in a database for future analysis. This device, known as the "automated trip hammer" (ATH), allows the automation and faster completion of a typically labour-intensive and slow testing process that can introduce human error and the risk of serious injuries.