Hamm Compaction Technology has introduced the "Vario-Control" intelligent compaction system for its HD+ 70 and HD+ 90 series tandem vibratory rollers. In road construction, the optimal vibration amplitude changes constantly: thin asphalt surface layers require low amplitude to prevent aggregate crushing, while thick aggregate base layers require high amplitude to achieve density. Traditionally, operators must stop the roller and manually adjust the eccentric masses on the drum shafts to change the amplitude, leading to downtime and human error.
The Vario-Control system replaces the mechanically fixed eccentric masses with a "Hydraulically Actuated Counter-Rotating Eccentric Mass Assembly" inside the drum. The engineering innovation is the "Soil Stiffness Feedback Loop." An accelerometer mounted on the drum bearing housing measures the rebound acceleration of the drum after each impact. The ECU calculates the dynamic soil modulus (stiffness) in real-time.
If the system detects that the soil stiffness is increasing rapidly (indicating the material is reaching optimal density), it automatically commands the hydraulic servo inside the drum to rotate the eccentric masses out of phase. This reduces the centrifugal force (amplitude) progressively, transitioning the drum from heavy impact to a gentle "high-frequency, low-amplitude" finish mode without the operator stopping. Crucially, if the roller passes over a soft spot (low stiffness), the system instantly increases the amplitude to maximum to force the material into place. This closed-loop amplitude control increases compaction throughput by 20% and completely eliminates the risk of over-compacting asphalt, which causes micro-cracking and premature road failure.
