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| robotic:tracked [2022/04/25 02:22] – tony | robotic:tracked [2026/09/26 22:02] (current) – [Conclusion] tony |
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| ===== Overview ===== | ===== Overview ===== |
| Experimentation with //[[:robotic:turbo|Turbo Explorer]]//, my first attempt at using the Dagu //[[:robotic:explorer|Explorer]]// robot control board, was halted as one of the motors died. But my brother had bought a tracked vehicle chassis that he could no longer use, so I transferred the electronics across. | Experimentation with //[[:robotic:turbo|Turbo Explorer]]//, my first attempt at using the //Dagu// //[[:robotic:explorer|Explorer]]// robot control board, was halted as one of the motors died. But my brother had bought a tracked vehicle chassis that he could no longer use, so I transferred the electronics across. |
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| ===== Hardware description ===== | ===== Hardware description ===== |
| {{:robotic:explorer:dsc_0200a.jpg?300|Base plate cut to size}} {{robotic:explorer:dsc_0201a.jpg?300|Base plate with mounting bolts}} | {{:robotic:explorer:dsc_0200a.jpg?300|Base plate cut to size}} {{robotic:explorer:dsc_0201a.jpg?300|Base plate with mounting bolts}} |
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| The chassis has two geared motors but instead of both driving from the same end, one is mounted at the front and the other at the rear. This means that the chassis assembly can be narrower than the width needed for two motors and gearboxes on the same axle. As with the //Turbo explorer// the motors must be wired run in opposite directions (ie one clockwise, the other counter clockwise) for the robot to move in a straight line. The motors are rated at 12V, but work ok from the 7.2V motor supply on the //Explorer// board. | The chassis has two geared motors but instead of both driving from the same end, one is mounted at the front and the other at the rear. This means that the chassis assembly can be narrower than the width needed for two motors and gearboxes on the same axle. As with the //Turbo Explorer// the motors must be wired run in opposite directions (ie one clockwise, the other counter clockwise) for the robot to move in a straight line. The motors are rated at 12V, but work ok from the 7.2V motor supply on the //Explorer// board. |
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| The plastic tracks ride over most surfaces without trouble and grip well enough to climb over small obstacles, although there is a tendency for the robot to be flipped upside down if it tries to climb over anything too high. Turning by rotating the two tracks in opposite directions works well on a smooth floor, but the 7.2 volt supply is under-powered for turning on rough surfaces such as carpet or grass. | The plastic tracks ride over most surfaces without trouble and grip well enough to climb over small obstacles, although there is a tendency for the robot to be flipped upside down if it tries to climb over anything too high. Turning by rotating the two tracks in opposite directions works well on a smooth floor, but the 7.2 volt supply is under-powered for turning on rough surfaces such as carpet or grass. |
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| =====Assembled robot====== | ===== Assembled robot ===== |
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| For the motors, the //Explorer// board uses 2 pin Molex connectors the same as found in many PC power supplies (internal plug connecting the mains wires, c0mes with high current wires attached). I modified an 8 AA cell battery pack to accommodate just 6 AA cells to provide a 7.2 to 8.4V battery for the system, found a plug (ex PC speaker I think) that matched the //Explorer// power jack. Strangely the //Explorer// board has large-pinned sockets for the outgoing power to the motors, but only a tiny battery socket through which all that power has to come! | For the motors, the //Explorer// board uses 2 pin Molex connectors the same as found in many PC power supplies (internal plug connecting the mains wires, c0mes with high current wires attached). I modified an 8 AA cell battery pack to accommodate just 6 AA cells to provide a 7.2 to 8.4V battery for the system, found a plug (ex PC speaker I think) that matched the //Explorer// power jack. Strangely the //Explorer// board has large-pinned sockets for the outgoing power to the motors, but only a tiny battery socket through which all that power has to come! |
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| =====Software===== | ===== Software ===== |
| I started with the Arduino code that I used on //Turbo Explorer//, but changed all turning routines to drive the motors on either side in opposite directions, rather than just letting on side idle while the other powered the turn. Otherwise the tracks on one side were dragged around as the other powered the turn. | I started with the Arduino code that I used on //Turbo Explorer//, but changed all turning routines to drive the motors on either side in opposite directions, rather than just letting one side idle while the other powered the turn. Otherwise the tracks on one side were dragged around as the other powered the turn. |
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| {{:robotic:explorer:explorer3.ino|Avoid obstacles}}: Initial basic "navigation" software, the objective is to be able to drive around a room without banging into things. It just uses the front corner sensors looking for things at close range, if it detects something it turns away in the opposite direction. If it detects something on both sensors it turns around. Additionally if it has been running without turning at all for 7 seconds it guesses that it might be stuck, and turns around. | {{:robotic:explorer:explorer3.ino|Avoid obstacles}}: Initial basic "navigation" software, the objective is to be able to drive around a room without banging into things. It just uses the front corner sensors looking for things at close range, if it detects something it turns away in the opposite direction. If it detects something on both sensors it turns around. Additionally if it has been running without turning at all for 7 seconds it guesses that it might be stuck, and turns around. |
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| This code doesn't use information from the rear sensors, even if it is backing up, so is prone to bumping into things when maneuvering. It also doesn't use info about motor current consumption even though this is readily available - this data could be used to detect wheel spin or a stall. The plastic tracks tend to slip on smooth surfaces when the robot has been stopped by some obstruction that it hasn't detected (eg something below the sensors or non reflective). Carpeted surfaces are hard for the tracks to turn on, but even there the tracks still spin rather than stall the motors.. | This code doesn't use information from the rear sensors, even if it is backing up, so is prone to bumping into things when maneuvering. It also doesn't use info about motor current consumption even though this is readily available - this data could be used to detect wheel spin or a stall. The plastic tracks tend to slip on smooth surfaces when the robot has been stopped by some obstruction that it hasn't detected (eg something below the sensors or non reflective). Carpeted surfaces are hard for the tracks to turn on, but even there the tracks still spin rather than stall the motors.. |
| =====Conclusion===== | ===== Conclusions ===== |
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| ====== References and Additional Resources ====== | ====== References and Additional Resources ====== |
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