Conveyor Belt Torque Control for Tension Prevention
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Solution Overview
Problem
Conveyor systems experience unwanted belt tensioning and snapping back when changing speed, leading to material stress and inefficiency, despite existing methods to smooth speed transitions.
Innovation Solution
Control the torque acting on the drive drum continuously within a defined time window, rather than specifying rotational speed, to gently accelerate or decelerate the belt, ensuring the torque decreases monotonically to zero at standstill, avoiding tension and snapping back.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the speed of the belt is changed using frequency converter with smoothed speed characteristic, then the torque impacts on the material are reduced, but the belt still experiences unwanted tensioning and snapping back
Solution Approach 1:
Instead of controlling the speed of the drive drum as in prior art, the invention inverts the control approach by directly controlling the torque acting on the drive drum. This inversion allows the torque to be continuously adjusted within a time window, preventing belt tensioning while achieving gentle acceleration or deceleration without the snapping back effect.
Solution Approach 2:
The invention applies dynamic torque control where the torque is continuously adjusted within a time window defined by first and second speeds. The torque control is adaptive and dynamic, ensuring smooth transitions and preventing abrupt changes that cause belt tensioning, while the time window duration is adjusted based on the specific operating conditions.
2Power
If the torque is abruptly set to zero at converter switch-off, then the motor stops driving the belt, but the belt snaps back due to stored tension
Solution Approach 1:
The invention applies preliminary action by controlling the torque to decrease monotonically to zero within the time window before the converter is switched off. This preliminary torque reduction prevents the belt from snapping back, as the torque is already at zero or near-zero when the converter switches off, eliminating the sudden force change that would cause snapping back.
Solution Approach 2:
The invention maintains continuity of useful action by ensuring the torque acts continuously and monotonically decreasing within the time window. The torque control is continuous and smooth, preventing abrupt changes and ensuring the belt decelerates gently without tensioning or snapping back, while the converter can be switched off at the appropriate moment.
3Reliability
If the return times and smoothing times are adjusted to avoid belt tensioning, then the belt snapping back is reduced, but the speed change becomes less efficient
Solution Approach 1:
The invention changes the control parameter from speed to torque, allowing for more precise and efficient control. By controlling torque within a time window rather than adjusting speed profiles, the system achieves better tension control while maintaining efficient speed changes. The time window parameter is optimized to balance tension prevention with change efficiency.
Data Source
Figure 1
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AI summary
The invention relates to a method for operating a conveyor system (2) with a belt (4) and at least one drive drum (6) for driving the belt (4), in which the torque (M) acting on the drive drum (6) is controlled to change the speed of the belt (4) within a time window (Δt) defined by a first rotational speed (n1) of the drive drum (6) and a second rotational speed (n2) of the drive drum (6). The invention also relates to a conveyor system.