| | 1 | = WAM Accuracy and Repeatability Study = |
| | 2 | |
| | 3 | == Repeatability Test == |
| | 4 | |
| | 5 | {{{ |
| | 6 | #!div class="center" align="center" |
| | 7 | [[Image(htdocs:wam/accuracy/wam_moving_towards.jpg)]] |
| | 8 | |
| | 9 | '''Figure 1: WAM arm moving towards dial indicator''' |
| | 10 | }}} |
| | 11 | |
| | 12 | {{{ |
| | 13 | #!div class="center" align="center" |
| | 14 | [[Image(htdocs:wam/accuracy/wam_touching.jpg)]] |
| | 15 | |
| | 16 | '''Figure 2: WAM arm touching dial indicator''' |
| | 17 | }}} |
| | 18 | |
| | 19 | {{{ |
| | 20 | #!div class="center" align="center" |
| | 21 | [[Image(htdocs:wam/accuracy/encoder_scale.jpg)]] |
| | 22 | |
| | 23 | '''Figure 3: Motor encoder scale''' |
| | 24 | }}} |
| | 25 | |
| | 26 | Encoder resolution: 40,000 counts/rev |
| | 27 | Motor resolution: 0.009 deg/count |
| | 28 | Joint 1 transmission ratio: 30:1 |
| | 29 | Ideal joint resolution: .0003 deg/count |
| | 30 | Approximate moment arm: 1 m |
| | 31 | Ideal repeatability: 0.005 mm |
| | 32 | |
| | 33 | === Repeatability Data === |
| | 34 | |
| | 35 | {{{ |
| | 36 | #!div class="center" align="center" |
| | 37 | [[Image(htdocs:wam/accuracy/repeatability_data.png)]] |
| | 38 | }}} |
| | 39 | |
| | 40 | == Accuracy Test == |
| | 41 | |
| | 42 | {{{ |
| | 43 | #!div class="center" align="center" |
| | 44 | [[Image(htdocs:wam/accuracy/single_link_pen.jpg)]] |
| | 45 | |
| | 46 | '''Figure 4: WAM - single link''' |
| | 47 | }}} |
| | 48 | |
| | 49 | {{{ |
| | 50 | #!div class="center" align="center" |
| | 51 | [[Image(htdocs:wam/accuracy/single_link_closeup.jpg)]] |
| | 52 | |
| | 53 | '''Figure 5: Closeup of single link WAM''' |
| | 54 | }}} |
| | 55 | |
| | 56 | {{{ |
| | 57 | #!div class="center" align="center" |
| | 58 | [[Image(htdocs:wam/accuracy/dual_link.jpg)]] |
| | 59 | |
| | 60 | '''Figure 6: WAM - dual link''' |
| | 61 | }}} |
| | 62 | |
| | 63 | === Notes regarding accuracy data: === |
| | 64 | It is important to note that the repeatability data is a better measure for calibrated accuracy than is uncalibrated accuracy. Uncalibrated accuracy was measured as shown in the figures to the right. A pen attached to the outer link was used to plot points on paper taped to the floor and the WAM base was secured to the floor. |
| | 65 | |
| | 66 | Potential sources of measurement error include: |
| | 67 | * the floor was assumed to be flat |
| | 68 | * physical measurement error with rulers & T-squares |
| | 69 | * physical measurement of WAM origin difficult to measure accurately |
| | 70 | |
| | 71 | Sources of system error (calibration error) include: |
| | 72 | * transmission ratio errors |
| | 73 | * tolerance stack-up of parts |
| | 74 | * tool location measurement (tip of pen) |
| | 75 | |
| | 76 | === Accuracy Data === |
| | 77 | |
| | 78 | {{{ |
| | 79 | #!div class="center" align="center" |
| | 80 | [[Image(htdocs:wam/accuracy/accuracy_vs_reach.png)]] |
| | 81 | }}} |
| | 82 | |
| | 83 | {{{ |
| | 84 | #!div class="center" align="center" |
| | 85 | [[Image(htdocs:wam/accuracy/graphs.png)]] |
| | 86 | }}} |
| | 87 | |
