Waste removal was and is an essential task for the survival of modern civilization. One such area is the underground sewage system, which is responsible for drawing off surface water and transporting wastewater to the sewage treatment plant. Any damage in this area can lead to both wash-outs and flooding of roads as well as contamination of the soil or groundwater. For this reason, many sewage regulations require drain inspections to be conducted at regular intervals. To take stock of the underground situation and check for any damage, the Kiel-based company IBAK developed a mobile inspection system with very compact dimensions, the centerpiece of which is a miniature telecamera. Drainage experts worked with FAULHABER microdrive specialists to come up with the ideal configuration. Several tiny motors with transmission attachments now move the camera so that the operator can view the system from any angle.
Estimates suggest the true total in Germany is closer to 1 million km of drainage. All of these underground pipes and channels are subjected to several different pressures at the same time: “interior assault” or corrosion, due to chemical and biological reaction of the water with the pipe walls, and external impacts such as traffic vibration or ground subsidence. There is also interference from tree roots causing damage to the seals, or cracks in walls that can make even the strongest pipe walls burst. Sooner or later this leads to damage that has to be repaired as quickly as possible. Repair work on sewage systems can be very costly and time-consuming, and in many cases also cause major disruption to traffic above ground. The more accurately the extent of the damage can be identified and localized in advance, the better any repair work can be planned and carried out. With the help of IBAK inspection systems, it is possible to have the camera travel the full extent of the sewage systems, checking and documenting the condition of all pipes and components along the way.
In addition to the requisite telecamera, a modern inspection system normally comprises a carriage that allows the camera to make its way through the pipes. To illuminate the visual field, IBAK cameras also have an integrated lighting element. For use in pipes with large diameters, IBAK offers additional headlamps that have greater reach. As well as lighting, plenty of electronic sensors form part of the “on board” equipment; they help determine the route to be taken through the underground pipes, in addition to providing objective measurement of any objects viewed along the way. A camera cable up to 500 meters long is used to supply the necessary power and data transmission. It connects the inspection system with the above-ground control terminal. Apart from this hardware, the inspector also requires extensive software so that the readings and images generated by the sensors can be accurately received and evaluated. The essential feature of any components used in underground drains is compact dimensions and a high degree of reliability. In the case of the ORION camera profiled here, this means the compact camera head must be able to move in all directions. The “neck muscles” to enable such 360-degree dexterity come from the three gear-motor units of the product range of FAULHABER. One motor is responsible for activating the (constant) turning motion of the head, the second performs the camera panning action and the third works as the focus motor to ensure the images are crystal clear. All three drives work independently of one another. For instance, whenever the operator has the video head pan up and down, the entire headpiece is also able to rotate around its longitudinal axis at the same time to reveal the contents of the whole pipe from all angles.
Small yet perfectly formed
The rotary drive moves the entire camera head. It uses a 12-mm-diameter motor with metal casing operating at around 0.5W and 6V. As a stainless steel, commutated DC motor, its speed is easily controlled via pulse width modulation (PWM). A 10-mm planetary gearhead with a reduction ratio of 256:1 scales back the overall speed and increases the output torque. Preloaded ball bearings minimize the play and allow for continual movement, which is very important for shudder-free filming. The swivel drive and focus are each run by an 8-mm-wide motor with a suitably compact gearhead. With around 0.2W power output and a reduction ratio of 1024:1 these drives facilitate delicate swiveling, panning and focus settings. Here, too, the emphasis is on precision and versatility. After all, the camera can only take as good an image as the angles set by the operator allow. Despite its tiny dimensions of no more than 8 to 12 mm, these motors work with an efficiency rating of more than 70% and 50% respectively. Compact, stainless steel, commutated DC motors combined with suitable gearheads offer ideal adaptation of the output speed to each particular use. The operator can also easily control the torque via simple pulse-width modulation. Preloaded, lightweight and long-life ball bearings in the motor and gearheads enable sensitive, smooth movements at rates of 0 revolutions per minute upwards. It means these miniature powerhouses are ideal for even the most demanding of tasks, where high continuity of speed or exact positioning is paramount.